An adjustable hinge for doors and windows comprising: - two hinge bodies (11, 12) for attaching respectively to a fixed frame and to a mobile frame of the door or window, - a revolving pin for pivotally connecting said hinge bodies (11, 12) to one another, - means for adjusting the mutual positions of said two hinge bodies(11, 12) in a direction crosswise to the axis of the pin, said means of adjustment comprising a sleeve, axially associated with said pin, defining an external lateral surface for coupling with a corresponding housing defined in a first of said hinge bodies (11, 12), said sleeve being pivotal inside said housing so that, while it remains constantly in contact with the walls (22a, 22b) of said housing during its rotation to change position, it can occupy substantially any position required along a limited length of said crosswise adjustment direction, means being provided for reversibly locking said sleeve in the positions it can occupy inside said housing by means of a thrust exerted in a given locking direction, characterised in that said sleeve comprises three distinct portions of contact with the walls of said housing, angularly spaced from one another by 120°, and when said locking means are in action at least two of the distinct contact portions bring a thrusting force, in directions incident to one another, on respective parts (22a, 22b) of said walls so as to take up any slack between the sleeve and the housing in incident directions, the thrust exerted by said locking means being decomposed into non-parallel directions coinciding with said at least two of said distinct contact portions; and in that the shape of said housing is symmetrical with respect to a longitudinal plane parallel to the axis of said pin inside the sleeve, and is formed with three different sliding grooves (22a, 22b) for corresponding contact portions, respectively two first grooves symmetrical with one another in relation to said plane, and one second intermediate groove between said two first grooves, said two first grooves being radiused at adjacent ends, while, at the opposite ends, they have abutments for said respective distinct contact portions serving as limit stops for the rotation of the sleeve, said locking direction defined by said reversible locking means on said sleeve lying on the plane of symmetry of said two first grooves. - two hinge bodies (11, 12) for attaching respectively to a fixed frame and to a mobile frame of the door or window, - a revolving pin for pivotally connecting said hinge bodies (11, 12) to one another, - means for adjusting the mutual positions of said two hinge bodies(11, 12) in a direction crosswise to the axis of the pin, said means of adjustment comprising a sleeve, axially associated with said pin, defining an external lateral surface for coupling with a corresponding housing defined in a first of said hinge bodies (11, 12), said sleeve being pivotal inside said housing so that, while it remains constantly in contact with the walls (22a, 22b) of said housing during its rotation to change position, it can occupy substantially any position required along a limited length of said crosswise adjustment direction, means being provided for reversibly locking said sleeve in the positions it can occupy inside said housing by means of a thrust exerted in a given locking direction,