In this paper the effects of channel estimation errors on spatial pre-coding schemes are analyzed. Under investigation is a novel pre-coding scheme with phase flipping, referred to as spatial phase coding (SPQ. The sensitivity of SPC to channel estimation errors in an OFDM system is compared to that of maximum ratio transmission (MRT), equal gain transmission (EGT) and transmit antenna selection diversity (SD). These diversity and pre-coding schemes have different requirements on the channel estimation and the feedback. Results are presented for a broadband OFDM system with two-dimensional pilot-symbol-aided channel estimation in a typical frequency- and time-selective propagation environment. It is shown that SPC is more robust to channel estimation errors than other spatial pre-coding schemes.