Abstract: A system for the detection of nitric oxide in a gas sample includes a converter for oxidation of nitric oxide to nitrogen dioxide, a nitrogen dioxide sensor including nanostructures and a filtering device to remove at least carbon dioxide from the gas sample positioned upstream of the converter. The nitrogen dioxide sensor can, for example, include a recognition layer on the nanostructures adapted to enhance sensitivity to nitrogen dioxide. A method for detecting nitric oxide in exhaled breath includes detecting nitric oxide in the exhaled breath using a nitric oxide sensor including nanostructures. Another method for detecting nitric oxide in exhaled breath includes filtering the breath to remove at least carbon dioxide from the breath, oxidizing nitric oxide in the exhaled breath to nitrogen dioxide and detecting the nitrogen dioxide using a nitrogen dioxide sensor including nanostructures.