The transport of charge carriers and the thermal diffusivity were studied on a set of polyaniline (emeraldine) samples that were compressed at various pressures, 50–1000 MPa. Marked correlations between the plots of compression pressure dependence of the electrical resistivity, the thermal diffusivity and the sample density were observed. This study has demonstrated that in order to obtain comparable data on samples prepared by compression of polymeric powders it is necessary to use sufficiently high pressure. In the case of polyaniline powder the pressure should be higher than 400 MPa. The values of the thermal diffusivity measured on polyaniline salt and its respective base indicate that charge carriers are not dominant in a heat-transport mechanism; only less than ten per cent of the thermal diffusion in pressed polyaniline samples can be eventually attributed to charge carriers.