In this contribution we present ab initio calculations of positron states and annihilation at vacancies and vacancy complexes in InN. Momentum distributions of annihilating electron–positron pairs in indium (VIn) and nitrogen vacancies (VN) as well as mixed vacancy clusters are calculated. Based on the modelled data the possibility of their experimental detection and distinction using positron annihilation spectroscopy is discussed. No localization of the positron density is found for isolated VN and VN clusters of up to 4VN. On the other hand, VIn and mixed vacancy clusters act as efficient positron traps in InN. While the calculated momentum distributions for the divacancy and VIn are quite close, mixed vacancy clusters which contain one VIn and two or more VN show well distinct spectra, that could be distinguished in suitable positron annihilation experiments.