  In this study we present abundances of 12^C, 13^C, N, O and up to 26 other
chemical elements in two first ascent giants and two core-helium-burning
'clump' stars of the open cluster NGC 2506. Abundances of carbon were derived
using the C_2 Swan (0,1) band head at 5635.5 A. The wavelength interval
7940-8130 A, with strong CN features, was analysed in order to determine
nitrogen abundances and carbon isotope ratios. The oxygen abundances were
determined from the [O I] line at 6300 A. NGC 2506 was found to have a mean
[Fe/H]=-0.24 +- 0.05 (standard deviation). Compared with the Sun and other
dwarf stars of the Galactic disc, mean abundances in the investigated clump
stars suggest that carbon is depleted by about 0.2 dex, nitrogen is
overabundant by about 0.3 dex and other chemical elements have abundance ratios
close to solar. The C/N and 12^C/13^C ratios are lowered to 1.25 +- 0.27 and 11
+- 3, respectively.
