Introduction. Evening primrose seeds are rich in linocetic acid. Leaf respiration (Lr) is the contrary process of leaf photosynthesis. The Objective was to establish if leaf respiration would be different for all the development phases of the evening primrose crop and affected by nitrogen fertilizations (Nf). Materials and methods. Evening primrose plants were planted in pots under three Nf (0, 80 and 160 kg N ha-1). Leaf respirations during the day (Lrd) and during the night (Lrn) were measured at all the development phases on plants of the three Nf. A CIRAS-2 infrared system was used to measure Lr on growing leaves. Results and analysis. Lrd and Lrn were higher at the first development phases and lower for the last phases. During the first development phases (rosette, elongation and flowering phases) Lrd was affected by Nf, while Lrn was only affected during the rosette phase. For all the rest development phases neither Lrd nor Lrn were affected by Nf. The differences for the development phases were probably produced by the high leaf nitrogen concentration (high concentration of mitochondria, chloroplasts and enzymes) observed at the beginning of the plant cycle. As it advanced the leaf nitrogen concentration receded reducing Lrd and Lrn. The Nf at the initial phases was able to increase Lrd and Lrn. Later, Nf did not affect them because the increase of leaf mass and the nitrogen redistribution from leaves. Conclusions. Leaf respiration is different for the development phases of the evening primrose crop. The leaf respiration during the day and the night were affected by the nitrogen fertilizations at the first development phases.