Comparative measurements by heat-flow microcalorimetry of the enthalpies of solution ΔHs(298.15 K) of CF3H(g) and of CF3Cl(g) have been performed in C6H6, C6H5CH3, p-C6H4(CH3)2, and 1,3,5-C6H3(CH3)3 in the mole mole-fraction range 5 × 10−5 ⩽ x < 2 × 10−3 of the solute, i.e. far below saturation at 0.1 MPa. From a shift of ΔHs of CF3H to more negative values by 3 to 5 kJ mol−1, compared with CF3Cl, a specific interaction of the polarized CH bond with the aromatic nucleus is revealed. An unexpectedly strong decrease of ΔHs by 5 to 7 kJ mol−1 at x < 0.001 was observed for all the solvents. This effect may be attributed to an increase of the positive contribution of cavity formation in the solvent to ΔHs from a minimum value at x = 0 to a maximum value according to the scaled-particle theory at x ≈ 0.001.