Abstract: A rotary ditching attachment for an articulated boom of an excavator type machine includes two rotary excavating heads supported in spaced relation on opposite sides of a central support. The heads rotate about a common axis. The rotary ditching attachment is rotatably coupled to the boom by a rotating tool mount. The rotating tool mount is connectable to the central support such that the central support and attached excavating heads are rotatable about an axis extending through the central support and perpendicular to the common axis of the excavator heads. Excavating assemblies are mounted on outwardly facing and inwardly facing surfaces of rotors forming each excavating heads. Rotating the rotary ditching attachment relative to a direction of movement of the rotary ditching tool relative to the ground increases the width of cut of the excavating heads when used to form or rehabilitate a ditch.