A side branch stent has a generally cylindrical body portion and a proximal split ring formed of a first semi-circular portion and a second semi-circular portion. The first semi-circular portion has a larger radius than the second semi-circular portion such that in a compressed configuration, the second semi-circular portion nests within the first semi-circular portion. Upon expansion of the side branch stent the two detached semi-circular portions expand to form a ring. The outer diameter of the proximal split ring, in both the compressed and expanded configurations, is larger than the outer diameter of the generally cylindrical body portion. The proximal split ring is used as a stopper or anchor which contacts the ostium of a vessel or the inner surface of a stent deployed in a main vessel of a bifurcated vessel in order to properly position the side branch stent in a side branch vessel.