In this work the location of a sample of 174 flux measurements (planetary nebulae, S,D,D′-type Symbiotic Star (SS) and six peculiar objects) on the λ5007/Hβ vs. λ4363/Hγ diagnostic diagram are compared, in order to investigate possible differences in electron density and temperature among them. Helium abundances, electron density and temperature were obtained for five D'-type SS and HD149427 (PC 11). In order to calculate them, expressions normally used for objects with low density were modified, in such a way that they can be used in objects with higher densities. © International Astronomical Union 2010.