An attachment for a mobile handling device is configured for processing walls or ceilings. The attachment comprises a mounting unit that is arranged to be supported at a mounting interface of the handling device, a processing head that is arranged to be equipped with at least one tool for material-removing processing or smoothing processing, and a compensation arrangement that is arranged between the mounting unit and the processing head and that defines a longitudinal axis. The mounting unit provides at least two pivot positions for the attachment that are offset from one another. The processing head is movable relative to the mounting unit in a longitudinal direction along the longitudinal axis. The compensation arrangement is configured to provide a defined contact pressure force for the processing head in a defined operating range along the longitudinal axis towards the surface to be processed.