I haven't tried it but DD loves fish esp. salmon.
The mom of her playmate dx'd w/ ADHD was taking supplements but she thought maybe they made him worse? He's a hard one, suspected PANDAS and such..
Anyway I'm going to throw in my environmental/chemcial input. There is a concern with mercury regarding fish, so I'd think you'd have to do a little research about the supplements before choosing.
Anyone check out this site?
http://apps.edf.org/page.cfm?tagID=16536&s_src=ggad_fishoil&gclid=CODAytHx4rACFSkRNAodgia0Jg