In this paper, we present a study of dual header-pulse interval modulation (DH-PIM) scheme for optical wireless communications. System theory and code properties of DH-PIM are discussed and expressions for the power spectral density, slow and packet error rates and optical power requirements are presented. The problem of baseline wander is also studied. The performance of DH-PIM is compared with other modulation schemes such as on-off keying (OOK), pulse position modulation (PPM), differential pulse position modulation and digital pulse interval modulation. We show that, DH-PIM offers higher bit rate and has a built-in frame synchronization capability. For a simple threshold detector receiver, it offers improved error performance compared with OOK, but marginally inferior performance compared with PPM. The optimum system performance in terms of optical power and bandwidth requirements is achieved at bit resolution of 5.