There is disclosed a device for cannulation of a hollow organ, in particular of an arterial or venous blood vessel of a mammalian body, e.g., human, said device comprising a cannula that has a proximal end, a distal end, and a central section located between the proximal end and distal end. The distal end has an expandable structure which can be converted, for example by means of a dilator, from a non-expanded state to an expanded state, and the expandable structure comprises openings at least in the expanded state.