This paper explains the air conditioning system and heat pumps on ships. Air conditioning is used to mantain a temperature and the moisture of the air at a desired level, disregarding the influence of the outside temperature and moisture. Heat pumps are devices which use renewable energy sources and thus with a high efficiency they perform the process of air conditioning (whether it be for cooling or heating). The best example of heat pumps being, of course, the air conditioner. Heat pumps are by far the most desirable, common and best air conditioning systems used on ships. First and foremost, the paper describes the process of air conditioning, as well as the air conditioning components. Pictures of the working principle of the cooling cycle, as well as the individual components of the evaporator, condenser, expansion valves and compressor are included . The basic theory of operation of the air conditioning components is provided. Apart from that, three improved cooling cycles are shown. Refrigerants which are used in the cooling cycle, providing insight into their classification, characteristics, usability, marking, physical properties and a way of the selection of the working substance. The aim of the second part of the paper is to explain and describe the types of air conditioning systems on ships: zone system, recirculation system and one-duct and two-duct systems. Lastly, the working principle of the heat pump and the overall heating system on the ship is described, all the while striving to substantiate the theoretical section of the paper with practical examples and images.