We consider two problems of constructing of goodness of fit tests for ergodic diffusion processes. The first one is concerned with a composite basic hypothesis for a parametric class of diffusion processes, which includes the Ornstein-Uhlenbeck and simple switching processes. In this case we propose asymptotically parameter free tests of Cramér-von Mises type. The basic hypothesis in the second problem is simple and we propose asymptotically distribution free tests for a wider class of trend coefficients.MSC 2000 Classification: 62M02, 62G10, 62G20.Key words: Cramér-von Mises tests, ergodic diffusion process, goodness of fit test, asymptotically distribution free.In the second problem we assume that under the basic hypothesis (H 0 ) the observed process satisfieswhere S 0 (·) is a known function, i.e., (H 0 ) is simple.In both models the alternatives are nonparametric and, under the hypothesis H 0 , the diffusion processes are assumed to be ergodic with the invariant densities f (ϑ, x) and f S 0 (x) respectively. We denote the corresponding distribution functions by F (ϑ, x) and F S 0 (x).Our goal is to construct the goodness of fit tests which provide the fixed limit error ε ∈ (0, 1). Introduce the class K ε of such tests, i.e., the testsψ T satisfying the relationsand limT →∞in the first and the second problems respectively. All tests studied in the present work are of the formψ T = 1I {∆ T >cε} , where ∆ T is the Cramér-von Mises type statistic. More precisely, in the first problem ∆ T is either of the L 2 distances D F T (x) , F θ T , x and