A combination of multi-input multi-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the performance of next generation wireless local area network (WLAN) systems. This paper evaluates the peak-to-average power ratio (PAR) performance in a MIMO OFDM-based WLAN system using a space-time block code (STBC). The investigated PAR control schemes, which are originally based on the selective mapping (SLM) and partial transmit sequence (PTS) approaches, select the transmitted sequence with the lowest average PAR over all transmit antennas and retrieve the side information (SI) very accurately at the expense of a slight degradation of the PAR performance. The low probability of false SI can improve the overall detection performance of the MIMO-WLAN system encountered with erroneous SI compared to the ordinary SLM and PTS approaches, respectively.