Thiosemicarbazones and their metal complexes attract constant scientific interest due to their antibacterial, antifungal and antitumor activities. In the recent years, a number of thiosemicarbazone derivatives have been synthesized and their biological activities were evaluated. Therefore, it is of interest to study the influence of thiosemicarbazide’s alkylation on the composition, structure and properties of transition metal complexes with these ligands. Isothiosemicarbazones have shown different coordination modes and are a potentially biologically active class of ligands because, compared with thiosemicarbazones,the alkylated sulphur atom remains uncoordinated at complexation in many cases with the exception of complexes of platinum metals. 2-hydroxybenzaldehyde4-allyl-S-methylisothiosemicarbazone 2-formylpyridine 4-allyl-Smethylisothiosemicarbazone The aim of this work is to find the conditions of synthesis and to determine the structure and biological properties of substituted salicylidene- and picolidene-4-allyl-Salkylisothiosemicarbazides. The structure and purity of the synthesized isothiosemicarbazones were confirmed using 1H, 13C NMR spectroscopy and also X-ray analysis. All peaks in the spectra of isothiosemicarbazones are double. It indicates the presence of tautomeric forms of isothiosemicarbazone in solution.Coordination compounds were obtained as a result of interaction between corresponding 3d metal salt and isothiosemicarbazone or by interaction of acetates of 3d metals and hydroiodide, hydrobromide or hydrochloride of corresponding isothiosemicarbazone. The in vitro antiproliferative activity of the isothiosemicarbazone and complexes was screened on human leukaemia HL-60, cervical cancer HeLa, pancreatic adenocarcinoma BxPC-3 and muscle rhabdomyosarcoma RD cells and normal MDCK cells. Some of the synthesized coordination compounds showed promising antiproliferative activity and low toxicity.