A counting detector is disclosed. In at least one embodiment, the counting detector includes sensors for converting radiation quanta into electrical pulses and an evaluation unit with a number of energy thresholds, wherein the evaluation unit generates for each sensor a count value for each energy threshold from the pulses, which count value represents the number of radiation quanta with an energy above the respective energy threshold. In at least one embodiment, one of the energy thresholds is arranged directly above a characteristic energy of radiation quanta causing double counting in order to correct double counting; and a correction unit calculates a corrected count value from the count values of the energy thresholds, which corrected count value has reduced double counting for at least one of the energy thresholds. Images with an improved contrast-to-noise ratio and, at the same time, a reduced X-ray dose can be generated on the basis of the at least one corrected count value. In at least one embodiment, the invention moreover relates to a computed tomography system with such a counting detector.