  We determine in a homogeneous way the metallicity and individual abundances
of a large sample of evolved stars, with and without known planetary
companions. Our methodology is based on the analysis of high-resolution echelle
spectra. The metallicity distributions show that giant stars hosting planets
are not preferentially metal-rich having similar abundance patterns to giant
stars without known planetary companions. We have found, however, a very strong
relation between the metallicity distribution and the stellar mass within this
sample. We show that the less massive giant stars with planets (M < 1.5 Msun)
are not metal rich, but, the metallicity of the sample of massive (M > 1.5
Msun), young (age < 2 Gyr) giant stars with planets is higher than that of a
similar sample of stars without planets. Regarding other chemical elements,
giant stars with and without planets in the mass domain M < 1.5 Msun show
similar abundance patterns. However, planet and non-planet hosts with masses M
> 1.5 Msun show differences in the abundances of some elements, specially Na,
Co, and Ni. In addition, we find the sample of subgiant stars with planets to
be metal rich showing similar metallicities to main-sequence planet hosts. The
fact that giant planet hosts in the mass domain M < 1.5 Msun do not show
metal-enrichment is difficult to explain. Given that these stars have similar
stellar parameters to subgiants and main-sequence planet hosts, the lack of the
metal-rich signature in low-mass giants could be explained if originated from a
pollution scenario in the main sequence that gets erased as the star become
fully convective. However, there is no physical reason why it should play a
role for giants with masses M < 1.5 Msun but is not observed for giants with M
> 1.5 Msun.
