In this paper, we characterize and compare a quantum dot and a quantum well lasers using the four-wave mixing analysis. The optical and power spectra of the four-wave mixing state in the quantum dot laser are studied both numerically and experimentally. The tendency of the amplitude versus detuning in the quantum dot laser is very similar to those seen in the quantum well laser. The four-wave mixing signals and the power spectra from both lasers are symmetric, while asymmetry in the regenerated signal is found. Compared to the quantum well lasers, the higher resonance peak of the regenerated signal of the quantum dot lasers appears on the opposite side of the detuning in the optical spectra. The intrinsic parameters of the lasers are also obtained by fitting the optical spectra and power spectra obtained experimentally with those derived directly from the rate equations. The measured value of the linewidth enhancement factor has a good agreement with that obtained by the injection locking method.