A microwave (MW) irradiation process was performed to pre-sintered CaCu3Ti4O12. A conventional furnace was used for calcination as well as for the sintering processes, whilst a domestic microwave oven was employed for MW irradiation in order to produce better morphology, improved phase structures and dielectric properties of CaCu3Ti4O12 products. SEM analysis shows that the microstructures of MW irradiated samples are denser, with larger grain size if compared to the untreated samples. Dielectric properties also have been improved by MW treatment with higher dielectric constant and lower dielectric loss. Meanwhile, the addition of tin oxide (SnO2) to CaCu3Ti4O12 provides strong effects on the dielectric constant of both without and with MW irradiated samples. it was found that the dielectric constant of CaCu3Ti4O12 decreases exponentially with mole percentages of SnO2. However, the addition of SnO2 shows better dielectric loss properties of CaCu3Ti4O12. (C) 2008 Elsevier B.V. All rights reserved.