Bu(2) and iso-Bu(2) phthalates were hydrogenated on Ni catalyst to resp. cyclohexane-1,2-dicarboxylates. The reaction product was analyzed by gas chromatography coupled with mass spectrometry. Beside of cis and trans isomers of the main product, the presence of small amts. (below 0.1% by mass) of BuOH, i-BuOH, Bu benzoates, cyclohexanecarboxylates and 2-methylbenzoates as well as phthalide of cyclohexane-1,2-dicarboxylic acid was evidenced.