Although retinal vein occlusion (RVO) has been known for about 150 years, and traditionally was assumed to be one entity, there are many arguments that RVO actually is not one disease. It has been suggested that it actually consists of six different clinical entities, each with different clinical characteristics, prognosis and management. For example, central retinal vein occlusion (CRVO) etiologically, clinically and from the management point of view is totally different from branch retinal vein occlusion (BRVO), and that is also true in the case of the major and macular retinal vein occlusions. Similarly, it is well-established now that CRVO is of two types, ischemic and non-ischemic, with very different clinical characteristics and management. It has also been shown that pre-existing ocular hypertension or glaucoma are important risk factors for CRVO and hemi-central retinal vein occlusion but not for BRVO. Many risk factors indicate systemic nature of some forms of the disease, although their real value remains speculative. Therefore, the lumping them together as one disease might be incorrect and misleading. Taking all above into account the traditional single disease model of RVO should be re-evaluated.