Finland is not part of Scandinavia.
Geographically Finland has a part of Scandinavia (now I mean the mountain range) in its land, so geographically yes, Finland is part of Scandinavia. But also geographically Denmark isn't part of Scandinavia which is just fucking retarded so when people refer to Scandinavian countries they mean at least Norway, Sweden, Denmark but also often Finland.
This comic shows how this thing actually works:
http://satwcomic.com/how-the-north-works.
So according to the comic Finland isn't part of the Scandinavian countries and therefore you're right according to the comic. HOWEVER as I told earlier people often include Finland into Scandinavia because they're too lazy to separate Scandinavia and Fenno-Scandinavia(or they don't know the difference, or they're not even aware that there is Fenno-Scandinavia). Finland has also been under Swedish rule. Usually Denmark, Sweden and Norway don't include Finland into Scandinavia (mostly because our language is very different and "Finns act so damn foolishly/stupidly/drunk/violent") UNLESS Finland does something prestigious.
So yeah, I'd say Finland is part of the Scandinavia. And now Svitjodvarg, lets not start fighting about this on this thread. I want to see more gifs and pics so PM me your respond if you wanna argue about this.