Abstract: A respiratory mask, in particular a nasal mask, comprising a mask body (1) with an internal chamber (10), an expansion part (2) being arranged on the mask body (1) and projecting upwardly from said mask body (1), said expansion part (2) comprising a traversing orifice (3), a holding arm (4) pivotable around a first axis (AA) located on said mask body (1) or on said expansion part (2), a forehead support (9) fixed to said holding arm (4) and pivotable around an axis (BB) located on said holding arm (4), and an acting piece (5) mobile in said traversing orifice (3), wherein the acting piece (5) cooperates with the holding arm (4) for pivoting said holding arm (4) around the first axis (AA) when said acting piece (5) moves in the traversing orifice (3) of the expansion part (2). The mask of the present invention is useable for treating sleep disordered breathing (SDB) conditions, such as, for example, obstructive sleep apnea.