Brain activity depends on GABAergic inhibitory interneurons. Dlx5 and Dlx6 are two closely related homeobox genes, expressed by the telencephalic ganglionic eminences. In the adult brain, Dlx5/6 are expressed in most cortical GABAergic interneurons.In the prefrontal cortex, Parvalbumin-positive neurons (PV-neurons) are involved in cognitive functions, and their maturation is critical for cognitive development. Using mouse lines in which Dlx5/6 are either invalidated or overexpressed in GABAergic neurons, we have recently shown that the adult density of PV-neurons is directly correlated to Dlx5/6 expression levels and that variations in Dlx5/6 expression affect adult anxiety and compulsive behaviours.In addition, PV-neurons play a crucial role in the postnatal maturation of the cerebral cortex, in the mouse. They are required for the progression a fundamental maturation process: the cortical critical periods (CPs). During the CPs, PV-neurons undergo sequential steps in their maturation: first the expression of Parvalbumin is activated, then the enwrapment of the cell bodies by the peri-neuronal net (PNN) a specialized extracellular matrix.Here we show that Dlx5/6 expression is required for the maturation of PV-neurons during the CPs affecting both Parvalbumin expression of and the formation of the PNN. Both the invalidation and the overexpression of Dlx5/6 impact these two critical steps of cortical maturation by inducing distinct region-specific alterations in PV-neurons density and causing PNN localized disorganization.We conclude that Dlx5/6 are involved in the genetic cascade controlling cortical maturation and CPs timing and might play a role in the adaptation to the environment during the postnatal period.