In this study, a series of new $N^2$ substituted 1,2-dihydro-3H-indazol-3-ones (3a-d) as well as their condensed pyrazolo, pyridazino derivatives such as pyridazino[1,2-a]indazole-6,9,11-triones (4a-h) and 3,9-dioxo-3H,9H-pyrazolo[1,2-a]indazole (7) were synthesized. The antiinflammatory activity of some synthesized compounds was determined by carrageenan-induced rat paw edema technique using diclofenac as reference drug. The pharmacological data showed that most of the tested compounds exhibited a significant long lasting antiinflammatory activity, which in the case of compound 3b was superior to that of diclofenac.