PURPOSE: We will present our mid-term result of transcatheter closure of PDA with Duct-Occlud device(pfm. AG. Germany) after 12 months follow up and report the problems during the procedure. METHODS: In total 154 patients, the Duct-Occlud devices were inserted in our institute from March, 1996 to August, 2002. Three types of Duct-Occlud device, i.e standard, reinforced, reinforced reverse cone coil were used. Echocardiographic examination was performed at 1, 6, 12 months after procedure. RESULTS: The echocardiographic closure rate was 96% after 12 months. The rates of residual shunt in the standard coil, the reverse cone coil, and the reinforced reverse cone group were 8%, 4% and 3% respectively. In PDA with diameter less than 4 mm, the closure rate was up to 98% while in large PDA with more than 4 mm, it was 72% after 12 months. Embolization of the inserted coils had occurred in 5 cases with successful retrieval using snare catheter. The rupture of the core wire during the procedure and distortion of the original coil shape had occurred in 4 cases. CONCLUSION: The transcatheter occlusion with Duct Occlud is safe and effective method for small to moderate sized PDA less than 4 mm. The minimum diameter of the PDA seems to be the predictor of residual shunt. Further refinement of the device to overcome the procedure-related problems seems to be needed.