The porosity that takes an important part in the failure process of three different ceramic materials (mullite, silicon carbide and silicon nitride) was characterised by means of Quantitative Image Analysis (QIA). Several parameters such as size, shape and orientation of pores have been evaluated. In parallel, the mechanical properties such as fracture toughness and Weibull modulus were directly measured. In order to appreciate the relevance of the use of QIA, the mechanical parameters have also been deduced from the microstructural features, and a comparison between measured and determined values was carried out. The results show a remarkable concordance.