The signal intensity of paranasal sinus mucocele is highly variable, ranging from high to low on both T1 weighted and T2 weighted sequence. This variation is likely due to the combined effects of decreases free water concentration, cross-linking and polymerization of the macromolecular mucus glycoprotein, and increased viscosity. We have experienced three cases of the paranasal sinus mucocele with different signal intensity on Magnetic Resonance Imaging. We describe MR characteristics of the paranasal sinus mucocele and compare with MR characteristics for other paranasal sinus diseases.