Ionospheric F2-layer disturbances not related to geomagnetic activity (Q disturbances) were analyzed using all available NmF2 observations over 26 Northern Hemisphere high-to-lower latitude ionosonde stations. Both positive and negative Q disturbances were revealed, their amplitude being comparable to moderate F2-layer storm effects. The occurrence of Q disturbances exhibits a systematic dependence on solar activity, season, and local time. Spatial variation pattern is different for positive and negative Q¿disturbances with the amplitude of the former increasing with latitude while the amplitude of the latter being practically latitudinal-independent. Longitudinal variations of the amplitude for both types of disturbances look like a planetary wave with minimal deviations in the American sector and maximal deviations in the European sector. Large longitudinal gradients in NmF2 can appear on the front of such waves.