To examine the anticancer activity several novel thiazolone-based compounds containing 5-aryl-3-phenyl-4,5-dihydro-1H-pyrazol-1-yl framework were obtained. Reaction of 5-aryl-3-phenyl-4,5-dihydropyrazole with 4-thioxo-2-thiazolidinone or 2-carbethoxymethylthio-2-thiazoline-4-one yielded starting 4- (1 and 2) or 2-substituted (11 and 12) thiazolones which were utilized in Knoevenagel condensation for obtaining a series of 5-arylidene derivatives 3-10, 13-18. Alternatively 11, 12 and their 5-arylidene derivatives were synthesized by means of 3-phenyl-5-aryl-1-thiocarbamoyl-2-pyrazoline as S,N-binucleophile via [2+3]-cyclocondensation approach. The structures of compounds were determined by (1)H, (13)C NMR, LC-MS, EI-MS and X-ray analysis. The in vitro anticancer activity of synthesized compounds were tested by the National Cancer Institute and most of them displayed anticancer activity on leukemia, melanoma, lung, colon, CNS, ovarian, renal, prostate and breast cancer cell lines. Relations between structure and activity are discussed, the most efficient anticancer compound 16 was found to be active with selective influence on colon cancer cell lines, especially on HT 29 (logGI(50)=-6.37).