Purpose : This study was to determine the relationship between age and the mandibular cortical bone thickness on panoramic radiograph. Materials and Methods : Panoramic radiographs of 360 patients (180 men and 180 women) over 20 years old, who visited the Chonbuk National University Hospital from January to December in 2007, were assessed. The subjects were divided into 5 age groups. Five indices such as cortical bone thickness at the gonion (GI), antegonion (AI), and below the mental foramen (MI), the panoramic mandibular index (PMI), the mandibular cortical index (MCI) were measured on panoramic radiographs. Results : All five indices including GI, AI, MI, PMI, and MCI showed significant differences between third decade and over 8 decade groups (p<0.05). PMI, MI and GI showed significant differences with gender statistically (p<0.05). Conclusion : The mandibular cortical bone thickness showed negative correlation with age, and the value of the thickness (PMI, MI, and GI) was greater in men than in women.