Finite-size scaling corrections in two-dimensional Ising and Potts ferromagnets

Finite-size corrections to scaling of critical correlation lengths and free energies of Ising and three-state Potts ferromagnets are analysed by numer ical methods, on strips of width N sites of square, triangular and honeycom b lattices. Strong evidence is given that the amplitudes of the 'analytical ' correction terms, N-2, identically zero for triangular and honeycomb Isin g systems. For Potts spins, our results are broadly consistent with this la ttice-dependent pattern of cancellations, though for correlation lengths no n-vanishing (albeit rather small) amplitudes cannot be entirely ruled out.