Polar substorms include substorms observed at geomagnetic latitudes above 70° MLAT in theabsence of simultaneous negative magnetic bays at lower latitudes, that is, substorms on the compressed contractedauroral oval. The general morphological features of polar substorms are considered based on theexample of individual events registered on Svalbard arch. It is shown that polar substorms, like “classical”substorms, are characterized by the formation of a substorm current wedge and a steplike movement to thepole after the onset of a substorm, generation of Pi2 geomagnetic pulsations, and an increase of the PC-indexof the polar cap before the onset of the substorm. At the same time, there are certain differences between polarsubstorms and “classical” substorms; namely, they start on more distant L-shells, develop in the region of acontracted auroral oval, occur at earlier pre-midnight hours, and generate only at low solar wind speeds andweakly disturbed geomagnetic conditions. It has been suggested that polar substorms may be a specific typeof “classical” substorms that develop in the evening sector under magnetically quiet or weakly disturbed conditionswhen the auroral oval is concracted. The source of polar substorms may also be a local intensificationof previously existing substorms in the post-midnight sector