Purpose: To study mid-term outcomes in patients admitted to receive treatment for acute type B aortic dissection. Methods: The study group comprised 229 patients with acute type B aortic dissection treated between January 2000 and July 2010. 128 patients had a thrombosed false lumen, and 101 had a patent false lumen. Results: In the thrombosed group, 6 had rupture, 4 had malperfusion, and 118 had no complications. There were 5 early deaths (3.9%). In the patent group, 12 had rupture, 19 had malperfusion, and 70 had no complications. There were 6 early deaths (5.9%). Overall survival rates in the thrombosed group and the patent group were 94.7 ± 2.2% and 90.2 ± 3.2% at 1 year, and 84.3 ± 4.6% and 85.9 ± 4.3% at 5 years (p = 0.892), respectively. Aorta-related event-free rates were 85.6 ± 3.4% and 48.3 ± 5.5% at 1 year, and 76.0 ± 5.1% and 35.2 ± 7.2% at 5 years (p <0.001), respectively. Conclusions: The incidences of rupture and malperfusion during the acute phase were higher in the patent group compared with the thrombosed group. At the late period, although the aorta-related event rate was higher in the patent group, the survival rate did not differ between two groups. Close follow-up and aggressive intervention strategy of the patent group may result comparable outcomes with the thrombosed group.