Tooth resorption (TR) is one of the most common dental diseases in cats. Determination of risk factors has not yet been fully assessed and, to the best knowledge of the authors, this disease has never been studied in Portuguese cats. The objective of this case-control study was to determine type and distribution of TR lesions, evaluate risk factors, and establish relationships between variables in this disease. The study included data from 71 cats admitted for general anesthesia for various reasons. The cats were randomly selected. The inclusion criteria were availability of clinical history and owner permission. Cats with known oral disease were not excluded from the study. All cats received ultrasonic scaling and polishing of the teeth, a thorough oral examination, and full-mouth radiographs. A strong statistical relation was found between age and TR. The age group of 10 to 15-years showed an increased risk of 6.56 times for TR occurrence compared with the group 0 to 4-years of age. Presence of gingivitis in all index levels was related to an increased risk for TR. No relation was found between age or gingivitis index and lesion type. Mandibular third premolar and molar teeth were most commonly affected by TR, especially for type 1 lesions. Canine teeth were statistically more likely to have type 2 lesions. The trend for the canine teeth to be more affected with type 2 lesions needs further verification.