The finding of a double primitive pulmonary neoplasm in the same patient is a fact rarely published, between 0.5 and 3.5% depending on the series, most of them surgical or necropsies series. We present the case of a patient who after being diagnosed of bronchial epidermoid carcinoma and treated with radiotherapy, developed, one year later, a relapsing homolateral pleural effusion due to an oat-cell type carcinoma. We review the incidence of this association in the scientific literature, outlining the difficulty to establish the diagnosis in patients non treated with radical surgery.