The present invention describes novel cyclic diol derivatives represented by formulae (I) and (II), in which Y represents O, S, SO, SO2, (CH2)m wherein m is 0 or an integer of 1 to 5, or NRa group wherein Ra is hydrogen, lower alkyl, lower alkoxycarbonyl, aryl, arylalkyl or acyl; R1 represents an alkyl or alkylcarbamoyl group; R2 represents a group having the formula: T-(CH¿2?)n-V(X?-¿)q, wherein T refers to a simple covalent bond, a CO, PO¿3?-, C(O)O, or CONRb group wherein Rb is hydrogen, lower alkyl or acyl; n refers to an integer of from 1 to 10; V represents either (i) the group indicated by the formula: -?+NR5R6R7¿ wherein R?5, R6 and R7¿ stand for identical or different lower alkyl group, or two or three of R?5, R6 and R7¿ taken together with the adjacent nitrogen form heterocyclic ammonio group, or (ii) the group indicated by formula (a) wherein R8 represents lower alkyl group; q is 1 or 0; X- represents a pharmaceutically acceptable anion. These compounds are potent PAF antagonists and thus useful for the treatment of the diseases in which PAF is involved.