We present a statistical analysis of a complete sample (255) of northern planetary nebulae (PNe). Our analysis is based on morphology as a main parameter. The major morphological classes are: round (26 % of the sample), elliptical (61 %), and bipolar (13 %) PNe. About a half of the round and 30 % of the elliptical PNe present multiple shells. Round PNe have higher galactic latitude (| b| = 12) and galactic height ( = 753 pc), than the elliptical (|b| = 7, = 308 pc) and bipolar (|b| = 3, =179 pc). This possibly implies a different progenitor mass range across morphology, as a different stellar population would suggest.