CHEMICAL-COMPOSITION OF SELECTED DOUBLE-MODE CEPHEIDS AND THE P-1 P-0[FE/H] RELATION/

We present the results of the detailed spectroscopic investigation of three double-mode Cepheids: EW Set, VX Pup and BQ Ser. The abundance a nalysis has shown: (1) Carbon is deficient (the abundance normalized t o the iron content with respect to the solar value). (2) This carbon d eficiency is accompanied by nitrogen overabundance and normal oxygen c ontent. (3) alpha- and iron group elements with little exception show solar ratio [M/Fe]. (4) The heavy elements in EW Set are underabundant . (5) Normal iron abundance for EW Set ([Fe/H]=-0.08) and metal defici ency for VX Pup ([Fe/H]=-0.39) and BQ Ser ([Fe/H]=-0.36) strongly supp ort the existence of a P-1/P-0-metallicity relation, as first discusse d in work of Andrievsky et al. (1993).