Multiple primary neoplasms (MPN) represent particular entities with growing impact in our daily practice due to their increasing incidence and implications in the treatment and outcome of oncological patients. MPN have a specific deffinition and can be classified as synchronous or metachronous depending on the time of diagnosis of the first and latter malignancies. We review in this article the possible risk factors involved in the etiology of MPN, the most frequent cancer associations, the incidence of synchronous and metachronous tumors, the stage at diagnosis, the treatment administered to the patients with MPN and the survival of patients with MPN.