The Korean grammar is very similiar to that of Japanese, and the syntax structure is almost the same, but there are many parts of the two languages that are completely different from each other, and THAT makes a lot of Korean learners of Japanese give up, and the same way around for Japanese people too. But the difference itself is very interesting if you keep studying, and for me, those differences are actually very good opportunities to think again and know more about my own mother tongue.
And there are lots of similar words between Japanese and Korean, too
I'm going out now but I'll write a posting on these similar words later and put a link here. ^_^