Two patients affected by appendiceal mucocele underwent emergency operation in our Department. Clinical findings and surgical management of the disease are discussed as well as controversy regarding the pathologic classification of the disease. The term "mucocele" is not referred to an exact histopathologic lesion: it describes the gross enlargement of the appendix, due to the accumulation of mucus in the dilated lumen. Currently such lesions are classified as nonneoplastic or as retention appendiceal cysts or as mucous-secreting tumours; the benign forms are cured by appendectomy, the malignant ones often require right colectomy for technical reasons. Pseudomyxoma peritonei significantly decreases survival of patients suffering from mucinous cystadenocarcinoma, but it does not affect survival in case of mucinous cystadenoma.