Colonization with Aspergillus sp. usually occurs in previously formed lung cavities. Cystectomy is a widely used surgical technique for hydatid lung disease that can also leave residual cavities and potentially result in aspergilloma. We present two cases of this rare entity and a case with Aspergillus sp. colonization of an existing ruptured hydatid cyst. (Ann Thorac Cardiovasc Surg 2008; 14: 116-118) aspergilloma, lung hydatid cyst, Aspergillus.