Capacitance is a property of biological membranes determined by the properties of the lipid portion of the membrane, as well as morphological features of a cell. In neurons, membrane capacitance is a determining factor of synaptic integration, action potential propagation speed and firing frequency. Besides slow changes associated with increased morphological complexity during postnatal maturation, neuron membrane capacity is largely considered a stable, non-regulated constant magnitude. Here we report that in pyramidal cells of mouse primary visual cortex the membrane capacitance changes nearly two-fold between the start and the end of a daily light cycle. The changes are large, nearly two-fold in magnitude in pyramidal cells, but do not affect cortical parvalbumin-expressing inhibitory interneurons. We discuss possible functional and practical implications as well as potential mechanisms.