Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity disorder induced by Aspergillus fumigatus that occurs generally in patients with asthma or structural lung disease such as cystic fibrosis. Generally, the diagnosis of ABPA is based on the criteria composed of clinical, radiological, and immunological features. As for the radiological respect of ABPA, it has very broad spectrum of imaging features. In fact, the physicians usually encounter the typical radiological findings such as bronchiectasis, mucoid impaction with finger-in-glove sign. However, the spectrum of radiologic features of ABPA is very broad, thus, in some cases, it is very difficult to distinguish ABPA from other respiratory disorders including lung malignancy. Here, we describe a case of small cell lung cancer developed in a patient diagnosed as ABPA completing the diagnostic criteria. Her radiologic finding was a mass like opacity with mucoid impaction, which did not response to the treatment for ABPA. Interestingly, re-pathologic examination revealed that the mass lesion was small cell lung cancer. This case shows the coexistence of ABPA and SCLC, which is a very rare condition and their prognoses conflict with each other, suggesting that although the diagnostic criteria is completed with patient`s features, when the disease progress is not usual, physicians should suspect other diagnosis actively and consider re-examination.