  Exoplanetary properties depend on stellar properties: to know the planet with
accuracy and precision it is necessary to know the star as accurately and
precisely as possible. Our immediate aim is to characterize in a homogeneous
and accurate way a sample of 27 transiting planet-hosting stars observed within
the GAPS program. We determined stellar parameters (effective temperature,
surface gravity, rotational velocity) and abundances of 26 elements
(Li,C,N,O,Na,Mg,Al,Si,S,Ca,Sc,Ti,V,Cr,Fe,Mn,Co,Ni,Cu,Zn,Y,Zr,Ba,La,Nd,Eu). Our
study is based on high-resolution HARPS-N@TNG and FEROS@ESO spectra and uniform
techniques. We derived kinematic properties from Gaia data and estimated for
the first time in exoplanet host stars ages using elemental ratios as chemical
clocks. Teff of our stars is of 4400-6700 K, while [Fe/H] is within -0.3 and
0.4 dex. Lithium is present in 7 stars. [X/H] and [X/Fe] abundances vs [Fe/H]
are consistent with the Galactic Chemical Evolution. The dependence of [X/Fe]
with the condensation temperature is critically analyzed with respect to
stellar and kinematic properties. All targets with measured C and O abundances
show C/O<0.8, compatible with Si present in rock-forming minerals. Most of
targets show 1.0<Mg/Si<1.5, compatible with Mg distributed between olivine and
pyroxene. HAT-P-26, the target hosting the lowest-mass planet, shows the
highest Mg/Si ratio. From our chemo-dinamical analysis we find agreement
between ages and position within the Galactic disk. We note a tendency for
higher density planets to be around metal-rich stars and hints of higher
stellar abundances of some volatiles for lower mass planets. We cannot exclude
that part of our results could be also related to the location of the stars
within the Galactic disk. We trace the planetary migration scenario from the
composition of the planets related to the chemical composition of the hosting
stars
