The 18th Symposium on Thermal Science and Engineering of Serbia entitled SIM-TERM 2017, organized by the Faculty of Mechanical Engineering in Nis and the Society of Thermal Engineers of Serbia, was held in the period from October 17 to 20, 2017, in the "Moravica" hotel in Sokobanja. This was the seventh consecutive time that the Faculty of Mechanical Engineering in Nis had the honor of organizing this Symposium, which is held every second year as a renowned international scientific conference. During SIMTERM 2017, 120 papers from Serbia and abroad were presented. Apart from the participants from Serbia, the papers were also presented by participants from a number of other countries (Italy, Russia, Turkey, Romania, Bulgaria, Macedonia, Slovenia, Croatia, Bosnia and Herzegovina, Germany, Kazakhstan, Montenegro). The Symposium took place in 8 sessions which included the following thematic areas: Technologies and Plants, New and Renewable Energy Sources, Mathematical Modelling and Numerical Simulation, Experimental Investigation of Processes, Energy Efficiency in Industry, Civil Engineering, Communal Systems and Traffic, Expert Systems, Fluid Flow, Heat and Mass Transfer, and Combustion, Environmental Protection, as well as several poster sessions. For this special issue of the journal Thermal Science has been prepared a selection of best papers presented at the 18th Symposium on Thermal Science and Engineering. Papers have been chosen and reviewed once again in accordance with the high standards of the journal Thermal Science.