Hypercapnia occurs rather often in clinic as an obvious determinant of gas exchange compromise. The causes of this phenomenon observed while general anesthesia, especially with the use of endotracheal intubation, may depend on the skill of anesthetist as well as type and condition of the equipment used. Maintaining adequate ventilation may be also difficult due to some central nervous system and respiratory tract ailments. The advantageous and adverse consequences of high paCO2 affecting the whole organism and particular organs were discussed in the work.