The present invention relates to a group of novel 4,5-dihydro-1H-pyrazole derivatives which are potent cannabinoid (CB.sub.1) receptor antagonists with utility for the treatment of diseases connected with disorders of the cannabinoid system. The compounds have the general formula (Ia) or (Ib) ##STR00001## wherein the symbols have the meanings given in the specification.The invention also relates to methods for the preparation of these compounds, and to pharmaceutical compositions containing one or more of these compounds as an active component.