— In receivers, IQ imbalances have significant effects on the performance of data transmission. Comparison of the performance of different types of Orthogonal Space-Time Block Codes (OSTBC) in the presence of IQ imbalances show that different codes don’t have a same behavior. Although most codes have an acceptable performance in low imbalances, they can’t work properly in the presence of intensive non-idealities. Despite this general similarity, there are some differences in the behavior of the codes against non-idealities. Such differences make them suitable for different situations. Keywords-MIMO; STBC; IQ imbalances; Mobile Communications