Visual selection requires mechanisms for representing object salience and for shifting the focus of processing to novel objects. It is not clear from computational or neural models whether these operations are carried out within same or different brain regions. Here, we use repetitive trans-cranial magnetic stimulation (rTMS) to briefly interfere with neural activity in individually localized regions of human posterior parietal cortex (PPC) that are putatively involved in attending to contralateral locations or shifting attention between locations. Stimulation over right ventral intraparietal sulcus (vIPS) impaired target discrimination at contralateral locations, whereas stimulation over right medial superior parietal lobule (mSPL) impaired target discrimination following a shift of attention irrespective of its location. This double dissociation is consistent with neuroimaging studies and indicates that mechanisms of visual selection are partly anatomically segregated in human PPC.