A bifurcation coronary lesion is defined as a lesion occurring at, or adjacent to, a significant division of a major epicardial coronary artery, being “significant” usually referred to a side branch (SB) of ≥2 mm in diameter, often arbitrarily defined based upon the subjective angiographic judgement of the operator [ ]. Nonetheless in the evaluation of a SB significance other important elements need to be considered including the extent of disease, bifurcation angle and size of the myocardial mass supplied.