The dependence of the hole spin relaxation on the electron density is studied in a n-modulation doped 75 Å GaAs/ AlGaAs quantum well by means of cw and time-resolved photoluminescence techniques. A slow hole spin relaxation time has been measured (~ 1 ns) and the polarization has been found to be strongly dependent on the in-plane wavevector of the photocreated holes. Calculations are presented which support the experimental findings.