Surface CNO and helium abundances predicted from 20 M_⊙ (with rotation, black lines) and 25 M_⊙ (with rotation in blue, without rotation in red line) evolutionary models are compared with observed surface CNO and helium abundances of Galactic blue supergiants, where N/C and N/O are number ratios, and Y_s is the mass fraction of helium at the surface. Solid parts of the lines indicate where radial pulsations are excited. Filled circles represent α Cyg variables, while open circles are for non-variable BSGs. Left panels: are for models with the Schwarzschild condition, right panels: are for models with the Ledoux condition.