Abstract: An adjustable radial flow diffuser for a radial flow compressor includes adjusting elements having diffuser blades. The adjusting elements are arranged in a diffuser annulus uniformly distributed along the diffuser circumference with an angular pitch .delta.. The adjusting elements further are swivellable about an adjusting axis V parallel to the longitudinal axis of the compressor for changing the narrow cross-section between the diffuser blades. The adjusting elements have either a substantially U-shaped or H-shaped cross-section with sector-shaped plates that are mounted on both sides of a blade root to form the legs. The diffuser blade forms the web of the substantially U or H shaped cross-section.