We present the [ X/H] trends as a function of the elemental condensation temperature TC in 88 planet host stars and in a volume-limited comparison sample of 33 dwarfs without detected planetary companions. We gathered homogeneous abundance results for many volatile and refractory elements spanning a wide range of T_C, from a few dozen to several hundred kelvin. We investigate possible anomalous trends of planet hosts with respect to comparison sample stars to detect evidence of possible pollution events. No significant differences are found in the behaviour of stars with and without planets. This is consistent with a "primordial" origin of the metal excess in planet host stars. However, a subgroup of 5 planet host and 1 comparison sample stars stands out as having particularly high [ X/H] vs. TC slopes.