Laser-induced fluorescence (LIF) imaging was applied to investigate NO formation in a directly injected diesel engine with realistic combustion chamber geometry. The technique, which uses KrF excimer laser excitation, was previously successfully applied in gasoline engines. Influences of interfering species depending on the spectral range used for LIF detection was investigated by spectrally resolved LIF detection. Laser and signal attenuation were assessed in sep. expts. using spectrally resolved O2-LIF detection with the same optical path as in the imaging measurements. The in-cylinder NO concn. was compared for different injection systems and operating conditions.