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 ( < { z } > = 753 pc ) , than the elliptical ( | { b } | = { 7 } ,~ { } < { z } > = 308 pc ) and bipolar ( | { b } | = { 3 } ,~ { } < { z } > = 179 pc ) .
This possibly implies a different progenitor mass range across morphology , as a different stellar population would suggest .