We have determined the Lande factor g* in self-organized InAs quantum dots using resonant-tunnelling experiments. With the magnetic field applied parallel to the growth direction z we find g*_parallel = 0.75 for the specific dot investigated. When the magnetic field is tilted away by theta from the growth axis, g* gradually increases up to a value g*_perp = 0.92 when B perp z. Its angular dependence is found to follow the phenomenological behaviour g* (theta) = sqrt{(g*_parallel cos(theta)^2 + (g*_perp sin(theta)^2}.