The present invention provides 1H-pyrazolo[4,3-b]pyridinesof formula (I) as PDE1 inhibitors and their use as a medicament, in particular for the treatment of neurodegenerative disorders and psychiatric disorders.本發明提供了作為PDE1抑制劑的具有式 (I) 之1H-吡唑并[4,3-b]吡啶及其作為藥劑特別是用於治療神經退行性障礙和精神障礙之用途。