In Colombian law, possession and retentíon have been classified in different fashions, including as mere legal facts, as a means of defense or even as veritable property rights. Beyond the terminological difficulties, this situa-tion has caused a real problem of legal uncertainty. For example, we may pose the questíons: do possession and retentíon enjoy general or special recognition? Under what conditions are these institutions valid? Do they offer direct powers over property? Do they provide some form of defense? Can they circuíate in the market? By way of introduction we will present i. a justification of the essay and ii. an initial approximation to the institutions of possession and retention.