Waste is any substance or object that the holder discards, intends to discard or must discard. There are two basic ways of separating waste, according to the place of origin and waste properties. According to the place of origin, waste is divided into municipal and industrial waste. According to the properties, waste is classified into: hazardous, non-hazardous and inert waste. Rapid industrial development and high technological progress are the main sources of an increase in waste materials. Improper waste management has led to environmental pollution and has had a serious impact on public health, so it is necessary to establish an efficient disposal system. As the amount of waste increases daily, it is important to improve the existing disposal mechanisms and to develop new ones. Mechanical biological treatment system – MBT is a waste treatment plant that combines two processes: mechanical (M) and biological (B) treatment (T) of waste. MBT plants are designed for the treatment of mixed municipal waste and industrial waste. The graduate thesis presents the influence of seasonal variations on average composition of municipal solid waste after treatment at the Marišćina Waste Management Centre. The purpose of the research was to determine whether there are significant differences in the basic geotechnical properties of residual waste from a winter and summer period. The conducted tests showed that the sample from a summer period contained a 7,6% higher share of organic matter, which means that the summer sample has a higher potential for biogas production. Deviations in the percentages of individual waste components according to the grain shape were also determined, which could have an impact on the amount of shear strength.