Chalcone derivatives of the general formula (I), wherein two from among A, B and Z which are adjacent to each other are linked and form a moiety selected from -O-(CH 2 ) n -S(O) m -, -S(O) m -(CH 2 ) n -O- and -O-(CH 2 ) n -O-, and the remaining one from among A, B and Z is H; or two from among A, B and Z, independently from each other, are selected from a group consisting of OH, -O-C 1 -C 6 -alkyl and -S(O)m-C 1 -C 6 -alkyl, and the remaining one from among A, B and Z is H; R is H, C 1 -C 6 -alkyl, carboxy-C 1 -C 6 -alkyl, -(CH 2 ) P - NR 1 R 2 or O(CH 2 ) 3 NH(CO)CF 3 , where R 1 and R 2 both independently are C 1 -C 6 -alkyl; or R 1 and R 2 are linked together to form polymethylene group -(CH 2 ) q -, and with N atom, to which they are attached, form a 5- or 6-membered ring, in which one of carbon atoms may be optionally replaced with O, N, or S; Y is -CH=CH-, -O-, -S- or -CH=N-; X 1 , X 2 , X 3 independently are H, halogen atom, OH, -C 1 -C 6 -alkoxy, carboxy-C 1 -C 6 -alkoxyl, di(C 1 -C 6 - alkyl)amino-C 1 -C 6 -alkoxy, -0-PO(OH) 2 , NO 2 or NH 2 ; m = O, 1 or 2; n = 1 or 2; p = 2 to 6; q = 4 or 5; and acid addition salts, salts with bases and C 1 -C 6 -alkyl esters thereof. The compounds may be useful as cytotoxic drugs for the treatment of neoplastic diseases. Formula (I).