The very rapid evolution of wireless telecommunications systems has led to public concern about the health hazards of electromagnetic energy. For many years, this question has been studied and the exposure limits have been established by such international organizations as ICNIRP and IEEE to protect the body from the hazards of exposure to RF electromagnetic fields. Before the use of portable personal wireless communication equipments was widespread, it was rare for a RF source to be located close to human head. Damages caused by electromagnetic field on biological tissues are thought to play role in temperature increase in cerebrospinal fluid, formation of cancers like brain tumors and ear tumors. It is aimed in this study to determine specific absorption rate (SAR) values created in human brain tissue by 900 MHz and 1800 MHz different antenna types. In the simulations helix and PIFA antenna structures are modeled using CST Microwave Studio. As a result of these simulations, SAR values were determined for different frequencies and antennas.