The Master-of-Science degree in computer science must include either the basic module in mathematics (according to the degree requirements of 2005, the extended module of at least 30 credits, and according to the degree requirements of 2008, at least 25 credits) or in method sciences (2005 degree requirements extended module of at least 30 credits and 2008 requirements at least 25 credits). The contents of the modules are described in more detail in the degree requirements.
It is best to start taking maths from your first year and complete most of the required credits during your first two years. Mathematics skills will be necessary for completing many computer science courses, especially from the third year on.
In addition to the compulsory course Introduction to discrete mathematics, you will find courses in analysis, algebra and linear algebra, and logics and probability calculus useful.
Studying mathematics and course line-up (on the website of the Department of Mathematics and Statistics)
Hints for studying maths (on the student organisation TKO-äly’s website, in Finnish)