Abstract: A class of pyrido[2,3-d]pyridazine derivatives, possessing an optionally substituted cycloalkyl, phenyl or heteroaryl substituent at the 8-position, a substituted alkoxy moiety at the 2-position, and a range of substituents at the 3-position, are selective ligands for GABAA receptors, in particular having high affinity for the &agr;2 and/or &agr;3 and/or &agr;5 subunit thereof, and are accordingly of benefit in the treatment and/or prevention of adverse conditions of the central nervous system, including anxiety, convulsions and cognitive disorders.