Crystalliser for continuous casting of billets and blooms, including a monolithic tubular structure whose transverse section defines the section shape of the cast product, said tubular structure including a wall defined by an outer face and an inner face located in contact with the cast metal, said crystalliser including holes for the transit of cooling liquid, made in the thickness of the wall of the monolithic tubular structure, said holes being made on said wall in such a manner that the distance ("d") between their longitudinal axis and the inner face of the wall of the crystalliser is between 5 and 20 mm.