Arrangement through which a process fluid is able to flow along a main flow direction, comprising an impeller which is rotatable about an axis in a direction of rotation, and an upright diffuser which is situated downstream of the impeller and is equipped with guide vanes, wherein the impeller has an inlet for a substantially axial inflow and has an outlet for a substantially radial outflow, wherein radially and axially extending rotor blades are arranged between a wheel disc and a cover disc of the impeller and delimit impeller channels with respect to one another in a circumferential direction, wherein the diffuser extends substantially radially along a main flow direction, wherein the diffuser has an axial cover-disc side and an axial wheel-disc side, which delimit between them an axial channel width of the diffuser, wherein the diffuser has a diffuser inlet for a substantially radial inflow and has a diffuser outlet, wherein guide vanes extending axially along a vane height direction and radially along a throughflow direction are arranged between the wheel-disc side and the cover disc-side of the diffuser and delimit guide-vane channels with respect to one another in a circumferential direction, wherein, for each axial vane height, an inlet-edge angle is defined as the angle between an inlet-edge tangent to a mean line at an inlet edge of the respective guide vane and a circumferential tangent through the inlet edge, wherein the inlet-edge angle is smaller on the cover-disc side than on the wheel-disc side, and wherein the inlet-edge angle is in this case the mathematically positively covered angle from the circumferential tangent to the inlet-edge tangent, characterized in that the guide vanes are designed such that a curvature angle between a tangent to the mean line in the inlet-edge region and a tangent to the mean line in the outlet edge region is smaller on the cover- disc side than on the wheel-disc side, wherein the curvature angle is in this case an angle which is measured in the mathematically positive sense proceeding from the tangent to the mean line in the inlet-edge region. wherein the impeller has an inlet for a substantially axial inflow and has an outlet for a substantially radial outflow, wherein radially and axially extending rotor blades are arranged between a wheel disc and a cover disc of the impeller and delimit impeller channels with respect to one another in a circumferential direction, wherein the diffuser extends substantially radially along a main flow direction, wherein the diffuser has an axial cover-disc side and an axial wheel-disc side, which delimit between them an axial channel width of the diffuser, wherein the diffuser has a diffuser inlet for a substantially radial inflow and has a diffuser outlet, wherein guide vanes extending axially along a vane height direction and radially along a throughflow direction are arranged between the wheel-disc side and the cover disc-side of the diffuser and delimit guide-vane channels with respect to one another in a circumferential direction, wherein, for each axial vane height, an inlet-edge angle is defined as the angle between an inlet-edge tangent to a mean line at an inlet edge of the respective guide vane and a circumferential tangent through the inlet edge, wherein the inlet-edge angle is smaller on the cover-disc side than on the wheel-disc side, and wherein the inlet-edge angle is in this case the mathematically positively covered angle from the circumferential tangent to the inlet-edge tangent, characterized in that the guide vanes are designed such that a curvature angle between a tangent to the mean line in the inlet-edge region and a tangent to the mean line in the outlet edge region is smaller on the cover- disc side than on the wheel-disc side, wherein the curvature angle is in this case an angle which is measured in the mathematically positive sense proceeding from the tangent to the mean line in the inlet-edge region.