Introduction: Periapical diseases are the final outcome of untreated pulpitis or failure of root canal treatment, collectively referred to as periapical lesions. Pulpitis is the final consequence of advanced dental caries or severe dental trauma, affecting the pulp. Spread of odontogenic infections into adjacent oral tissues and distinct structures by blood and lymph vessels can lead to more serious complications. Therefore, early and correct diagnosis and treatment of these lesions is necessary to prevent their potential complications. Considering the importance and high prevalence of periapical lesions, this study was undertaken to evaluate the periapical inflammatory lesions and spread of odontogenic infections.Review Report: In this study, studies performed from 2000 to 2013 about clinical, radiographic, and histopathologic features and treatment of periapical lesions, and also spread of odontogenic infections were evaluated by running a search in PubMed, EBSCO, ISC and Google Scholar databases.Results: Periapical periodontitis is one of the most common odontogenic diseases; the chronic type of it or periapical granuloma is more prevalent than its acute type or periapical abscess. Radicular cyst, the most common odontogenic cyst, is a sequela of periapical granuloma. Inflammatory lesions with an odontogenic origin can spread to the bone marrow, causing osteomyelitis. In addition, these lesions give rise to acute and serious diseases such as soft tissue abscesses and cellulitis if they are not managed on time.Early diagnosis of periapical lesions leads to easier management, more successful treatment and better prognosis.