Ni doped ZnO (Zn1-xNixO, in which 0.1 <= x <= 0.4) diluted magnetic semiconductor nanoparticles are prepared by microwave irradiated solvothermal process. The structural properties are studied using X-ray diffraction. It is evident from the XRD spectrum that the Ni doped ZnO nanocompounds exhibit single phase hexagonal wurtzite structure with strong c-axis orientation. To improve the crystalline quality the samples are annealed at 400 degrees C. The effects of annealing temperature and dopant concentration on the structural properties are also discussed. Unit cell expansion is clearly observed in Ni doped ZnO nanocrystals. The TEM images confirm that the particle size is 20 nm and the particles are well dispersed. The magnetic property of the nanocrystals was measured using vibrational sample magnetometer. According to the magnetization measurements ferromagnetic behavior was found in Zn0.9Ni0.1O combination. However, for the other higher dopant ratios paramagnetism is observed. (C) 2012 Elsevier B.V. All rights reserved.