Abstract. The aim of the research is to identify the effect of monochromatic and white lighting on the functional state of the liver of egg chickens during the growing period, taking into account the season of the year. Method of research. Laboratory diagnostics of blood of 30-, 60- and 90-day old young animals. Anatomical examination of the liver of a bird at the age of 15 weeks (70 carcasses of birds were used), using the decapitation method, histological examination of the liver (19 organs), using a light microscope Carl Zeiss. Results. In all seasons of the year, the number of hemoglobin in the blood increases by 14.6 %, red blood cells by 9.4 %, albumins by 15.8 %, high values of white blood cells decrease by 2.5 times, gamma globulins by 19.8 %, bilirubin by 37.3 %, triglycerides by 26.9 %, cholesterol by 34.6 %, and asparagine aminotransferase activity by 27.5 % and alanine at 37.7 %. In young hens under white light, the amount of epicardial fat is less by 13.0–78.1 %, abdominal fat by 30.5–64.9 %, than in birds with monochromatic lamps. Histological examination of the liver of hens containing in any light revealed chronic hepatitis. In birds by white and yellow lighting, the development of the inflammatory process is less pronounced, there is no significant increase in the size of the nucleus and cells of hepatocytes, the expansion of the lumen of blood vessels, the number of lymphoid follicles in the centre and intermediate zone of the liver lobes less is 36.2–55.7 %, than in young hens by green and blue (white-blue) lighting. Scientific novelty. The use of white and yellow compact fluorescent lamps with a color temperature of 4500–5500 K and 2800–3000 K, respectively, with a light flux of 400–800 LM in the poultry house, has a weak positive effect on the functional state of the liver of egg chickens during the the period of growing from the daily age to the age of 15 weeks in cells in conditions of gradually decreasing length of daylight hours and light level.