Abstract: There is a lack of biological studies using selenium and tellurium compounds, specially concern with cancer therapy. The aim of this study is to evaluate the cytotoxicity action of nine β-chalcogen-substituted Michael-aldol-type adducts on HeLa and RKO cancer cell lines. The cytotoxic effect was assessed by MTT assay and was performed in HeLa and RKO cell lines cultured in RPMI-1640 medium in (95% O2+5% CO2) at 37°C. The IC50 values demonstrated that all compounds presented cytotoxic effect in 17-100 μM range. The compounds 1 and 5 presented cytotoxic effect in 17 -40 μM range to HeLa cells. In RKO cells compounds 2-5, 7 and 8 presented cytotoxicity between 46 -58 μM. Compound 1 presented cytotoxicity for HeLa cells similar to those found to etoposide (11.35±2.73 μM; p>0.05) and none of the compounds presented this similarity for RKO cells. It is important to notice that the compounds presented cell line selectivity: compound 1 to HeLa and compounds 7 and 8 to RKO cells. The RKO cells were more sensitivity to tellurites, which were not effective to HeLa cells. In conclusion, the compound 1 presented promissory anticancer potential and the cytotoxic specificity of tellurides for RKO cells demonstrated that there is an important biological role based on this chemical element.