Thirty-three patients with anterior mediastinal masses underwent percutaneous ultrasonically guided needle biopsy (UGNB), including ultrasonically guided aspiration biopsy (UGAB) in all 33 patients and ultrasonically guided cutting biopsy (UGCB) in 13 patients. Using UGAB alone, the diagnostic rate of anterior mediastinal masses was 52% (17/33); if both the UGAB and UGCB methods were used, the diagnostic rate could achieve 79% (26/33). If the anterior mediastinal masses were divided into carcinomatous (n = 15) and non-carcinomatous (n = 18) groups, we found that the carcinomatous group was more easily diagnosed by UGAB than the non-carcinomatous group (87% vs 22%, p < 0.01) and UGCB was more valuable and helpful than UGAB in the diagnosis of non-carcinomatous mediastinal masses (75% vs 22%). One episode of injury to the aortic wall occurred after a UGCB. Our results show that carcinomatous mediastinal masses can be easily diagnosed by UGAB, and UGCB is often necessary in the diagnosis of non-carcinomatous mediastinal masses.