The solubility behaviors of polymethyacrylonitrile (PMAN), poly(methacrylic acid) (PMAA), and its random copolymer methacrylonitrile (MAN)/methacrylic acid (MAA) in various solvents were investigated. The results were used in a computer program to obtain a 3-dimensional representation of the polymer solubility region in the Hansen space. Thus, the values of dispersion (δd,p), polar (δp,p) and hydrogen bonding (δh,p) components of the total solubility parameter (δt,p) were obtained. Comparisons between the experimental results and the estimated values are discussed. Also, prediction for solubility parameter values for MAN/MAA copolymer via their homopolymers, PMAN, and PMAA has been evaluated.