Abstract: The invention provides 1,3,4-thiadiazoles and 1,3,4-oxadiazoles having the following Formula I: in which, Y is S or O, R1 is alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, cycloalkenyl, aryl, heteroaryl or a polycyclic group, optionally substituted, R2 is alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, cycloalkenyl or aryl optionally substituted, R3 is X2—R?3, in which X2 is a binding group and R?3 is cycloalkyl, heterocycloalkyl, cycloalkenyl, aryl, heteroaryl, or a polycyclic group; optionally substituted, or their pharmaceutically acceptable derivatives, a compound of Formula I, for their preparation, and processes for pharmaceutical compositions containing methods of using the compounds for the treatment of disorders for which a treatment by a PDE7 inhibitor is relevant.