Fine needle aspiration (FNA) is found to be a useful and non invasive technique in the presurgical diagnosis of intrathoracic masses. In the present study we report our findings from a total of 33 mediastinal aspiration punctures, performed over the past 24 months. In 24 of the 33 puntures, the lesion was either previously biopsied or surgically removed, which allowed for the corresponding cytohistological correlations. The cytological diagnosis demonstrated 12 cases of malignancy, 2 cases of benign lesions and 5 cases of negative tumours. It was possible to establish the cellular lineage in only 8 cases without specifying the benignity or malignancy of the lesion (2 neural tumours, 2 thymomas, 2 spindle cell mesenchymall tumours and 2 with a lymphoproliferative process), while 6 cases were insufficient for diagnosis. The sensitivity and specificity obtained using this diagnostic methodology was 79% and 100% respectively, where the diagnostic accuracy was 83%. The positive and negative predictive value was 100% and 53% respectively. In 2 of the 9 cases that were not operated on, the cytological diagnosis was benign, showing 2 brochogenic cysts that were evacuated during the process thus resolving the situation. Our findings and the adequate cytohistological correlation obtained confirm the effectiveness of FNA in the diagnosis of mediastinal masses.