Two series of 2-thioxoimidazo[4,5-b]pyridine derivatives have been synthesized from 2,3-diaminopyridine (1) and 5-halogenosubstituted-2,3-diaminopyridines 2, 3. Mannich bases 7 - 12 and 24 - 29, derivatives of 1-arylamino-6-halogeno-2-thioxoimidazo[4,5-b]pyridine were obtained with selected secondary amines: morpholine, piperidine, 2-methoxyphenylpiperazine, pyrimidyn-2-yl-piperazine and formaldehyde in ethanol. The structures 7 - 12 and 24 - 29 were confirmed by the results of elementary analysis and their IR, 1H-NMR and MS spectra. All given structures 7 - 12 have been optimized to get the most stable low energy conformers. Synthesized compounds were of interest for biological studies or can be substrates for further synthesis. The selected compounds 7 - 10, 12- 17, 22, 25, 27 - 29 were screened for their antiproliferative activity in vitro against human cancer and normal mouse fibroblast cell lines.