In this paper, the problem of target detection in phased-MIMO radars is considered and target detection performance of phased-MIMO radars is compared with MIMO and phased-array radars. Phased-MIMO radars combine advantages of the MIMO and phased-array radars. In these radars, the transmit array will be partitioned into a number of subarrays that are allowed to overlap and each subarray transmits a waveform which is orthogonal to the waveform transmitted by other subarrays. In this paper, target detection performance of phased-MIMO radars is analyzed with two detectors theoretically in addition to the investigation of simulation results. First, it is assumed that the transmitted waveforms are ideally orthogonal and secondly the transmitted waveforms are considered to be correlated (not fully coherent or ideally orthogonal). The Generalized likelihood ratio test (GLRT) and the likelihood ratio test (LRT) are used for target detection. The closed-form expressions of the false alarm and detection probabilities in presence of Gaussian noise are obtained. Simulation results validate the theoretical analysis.