Apical inflammatory root resorptions are frequently the result of long lasting chronical inflammation. Untreated, these situations can lead to loss of hard tissue and even the loss of the tooth. The management of these lesions consists of multi-visit canal treatment, with calcium-hydroxide as interappointment dressing and application of MTA. Single-visit treatment may be also an option. Our clinical cases show the importance of correct diagnosis of the apical inflammatory progressive root resorptions and the evaluation of the outcome of the endodontic treatment due to the use of cone-beam computing tomography (CBCT). The treatments proved to be successful. Although some of the root canal filling seem to be incomplete on radiographs, because of the oblique defect and the roots remained short, the functionality of the teeth could be preserved. Precise information influences the diagnosis and the treatment planning decision.