We have investigated the Zeeman splitting in strained In x Ga 1Ϫx As quantum dots with different quantization energies by means of magnetoluminescence. A multifold splitting of ⌸ and ⌬ states is observed due to lifted degeneracy of mϾ0 states. The experimental data were systematically compared to the diamagnetic and Zeeman shift of the single-particle states, taking into account the details of the valence-band structure and the spin splitting. Our data indicate that excitonic effects are negligible and that the magneto-optical properties of these strongly confined dots can be described rather accurately within the single-particle model. ͓S0163-1829͑98͒02116-X͔