We have studied the magnetic properties of nanocrystalline ceramics CuO with grain sizes 5-100 nm. Immediately following fabrication of nanoceramics the low-temperature contribution in magnetic susceptibility chisimilar to1/T was observed. The peculiarities of chi correlated with the grain sizes. The "paramagnetic" contribution below 140K disappeared after 3 years of storage. Temporal changes in the magnetic properties of CuO nanoceramics are discussed in connection with relaxation of defects and grain boundaries. (C) 2002 Elsevier Science B.V. All rights reserved.