To add to some of the points made above: in looking at the possible value of adding an addendum, you should also consider the possible costs--doing so might tend to focus attention on your cancellations. Also, law schools use the highest official score from each student in determining their class average LSAT score, so for the admissions office, the presence of a very solid score on your LSAT report will likely reduce focus on a couple of cancellations.

largely.
schools take the highest score, if cancellations are years apart, does it matter? I canceled in late '02 when I wasn't really serious and hadn't studied. I spent the next couple of years working random jobs and then canceled in early 06 after not having prepped fully. Just decided to take it again at that point but wasn't really happy with how I felt it went. Spent a few years in sales, didn't really think about law school. Then I took in September and did OK, scoring 162. Just cancelled Feb retake. Thought I could go higher, but really couldn't concentrate late in the test on games and ate it on the last two, guessing 9 times. Anyway, would I need to write an addendum? Many schools don't ask about all LSAT dates, while others do. Scores are supposed to be gone after 5 years. Advice?
The 2002 info is now wiped from your master record, so don't worry about that one.
Just so I'm straight on this, in the last five years this is your complete LSAT record:
Feb or June 2006 = cancel
September 2009 = 162
Feb 2010 = cancel
Let me know if that is correct and I'll comment further.
If your LSAC 'candidate report' Law School admission committees receive from LSDAS after you submit applications for them to evaluate you which span the last five years of your LSAT official history only shows one reported score of 162 and a cancellation or two, meaning that the fiascoes you had in the previous 8 year saga are things that have dropped off your record because they occurred prior to June 1, 2004 registrations, you are in good shape and I agree not to include an addendum that would draw attention to the matter.
"
The score report that is displayed online or mailed to you will show your current test results, along with the results of all tests—upto12—for which you registered since June 1,2004, including absences and cancellations. An average score is also calculated and reported when you have more than one reportable score."
As I said before, 162 is a very competitive highly percentile ranked score that gives you good admission chances to many T1/T2 Law Schools as long as your GPA is also within the middle-upper index range of those schools.
If your overall GPA is sub-par for the index range of the LS's you will apply to, you may consider explaining that if you have a legitimate reason for it (family crisis, mom died, got run over by a car and was in the hospital for a while, etc. But it has to be a serious reason, not some silly excuse)
If your cumulative GPA is sub-par but there is a major upswing during the two years leading up to graduation, you may consider addressing that. My overall GPA was not great due to my chem grades of a D and an F, plus I had little interest in the required 1st UG year humanities core (that class was a total sleeper and we were required to buy and read ~13 books. One of the proffs spent a lot of class time talking about the sex stuff plato or socrates and the people of the time did and he described the acts in detail!)
Your application materials should include a quality genuine/compelling personal statement with an interesting starter that grabs the readers attention so they will keep reading it, be interested in you and seriously consider it. Something that portrays you as a human and something more than two numbers.
LS adcomms receive and have to review thousands of apps adding up to thousands of pages. They only spend minutes reviewing each application due to volume and available hours per day. With a quick look they can smell common canned BS that does not pass the 'sniff test'.
You need good LOR's from respected sources that know you well and write something in detail -more than a few canned largely vague sentences- that demonstrates that they really know you and believe in your abilities.
Good LOR's should fill at lease 1/4-1/3 of a page and go into details about you to show that the person that wrote it knows you in order to justify the basis of the recommendation. Generic short LOR's that contain no details about you can actually hurt your admission chances.
The whole application package must paint a good true picture of you RE: what adcoms care about in terms of being a motivated capable
HUMAN BEING that really wants to go to LS that has the capability to put in the required work.
Even though some LS's seem to act as "number whores" basing decisions very heavily/mainly on applicants LSAT and GPA combination's alone as it applies to their numerical index formulas, which many do for ranking and indexing purposes, presenting compelling 'soft factors' in an application can make a
HUGE difference.
My UG GPA transcripts sucked.

I mean really, I got a D the first time I took Chem and did the re-take of the exact same class with the University policy that would delete and replace the first grade if I did better the seond time. I got an F the second time so they both showed!
Stoichiometry wasn't something I could get myself interested in and study at that time in my life, that stuff is complex, very dry and I was much more interested in chasing girls and going to tons of concerts and parties

.
I'm not going to describe how O-Chem went before I decided:
"WTF am I doing? 'F this bio major and med school idea. Mom, just cuz you are an NP with a masters degree and want one of your sons to get an M.D. does not mean I'm going to medical school."
Then I switched from a Bio degree to social sciences, earned a psychology degree followed later by a J.D. It was like getting home from a long tortuous journey after getting dragged through the desert.
A cliche phrase I love to use that there is truth behind "When you get lemons, make lemonade." When I applied to LS I built my PS around my interest in psychology and the law and got my LOR's written by renowned PhD's and M.D's (one was a Nobel Laureate) I had been working with in a Neuropsychology ward directly doing hands on research/clinical assessments of various mental patients. I did the face to face interviews and assessments of tons of patients being held in the ward and wrote up the clinical reports that resulted in articles being published in Oxford Journal, Schizophrenia journal and other places with my name as a published author in some of them.
http://schizophreniabulletin.oxfordjournals.org/cgi/reprint/25/3/577.pdfhttp://www.journals.elsevierhealth.com/periodicals/bps/article/S0006-3223%2898%2900115-2/abstractMy recalculated LSDAS GPA was 3.09 with a 177 LSAT score. I wrote multiple addendums, one explaining my sucky performance in the first 2 years of UG (having to explain about being put on academic probation due to my grades in Chem classes and in DNA/genetics class) as well as having to write one about an arrest and criminal prosecution.
After my arrest and almost getting kicked out of UCI I got serious and achieved pretty much straight A's the last two years along with getting multiple Deans notes/awards of excellence on my transcript.
With that weird record I was accepted to many T14 schools and others that offered scholarships. Some of them that accepted me were USC, Georgetown, Columbia, Cornell, as well as many lower ranked backup schools.
Georgetown offered me a scholarship for tuition for all 3 years (but I'm a Socal guy and would not be happy living in that area during the frigid winters, I like temp ranges of 65-73) so I declined.
I was offered full rides from numerous California LS's . I could have gone to Pepperdine LS with a full scholarship including room and board and the same thing with a few other LS's (some in the UC system in Northern CA)
To end my long story, even though they didn't offer any $$, I went with my #1 choice. USC (University of Southern California)

Fight on!