The authors report the spontaneous detachment of a coil during embolisation of a coronary fistula in a 34 old year woman with operated tetralogy of Fallot. The fistula originated from an isolated circumflex artery and drained into the infundibulum. By retrograde approach, a microcatheter was successfully advanced into the distal part of the fistula, one coil loop was fixed through the fistula mouth and two in its distal portion. During positioning of the proximal part of the coil, it suddenly detached into the microcatheter. Coaxial snaring of the coil was attempted, however this manoeuvre produced progressive elongation and repeated ruptures of the coil. Finally, the procedure was abandoned; surgical extraction of the coil and suture of the fistula were successfully performed. Percutaneous transcatheter closure of coronary fistulae, although generally feasible is burdened by complications due to tortuous anatomy, poor stabilisation of catheters and lack of specific materials.