Neutrophils constitute the first line of the innate immunity in humans. They employ several strategies to trap and kill microorganisms, such as phagocytosis, degranulation, and the formation of extracellular traps (NETs). It has been well documented, that generation of reactive oxygen and nitrogen species (ROS and RNS) is crucial in the life cycle of a polymorphonuclear phagocyte. These compounds due to high reactivity act as powerful antimicrobial factors in the process of pathogens clearance and can also modulate immunological response. On the other hand, excessive amount of free radicals may have detrimental effect on host tissues and markers of oxidative and nitrosative stress are detectable in many diseases. It is necessary to maintain the balance between ROS/RNS formation and removal. The review highlights our current understanding of the role of ROS and RNS produced by neutrophils in health and disease.