Carbon monoxide (CO) remains an insidious and silent killer due to its physical and chemical properties; its lethal effects are encountered in cases of household accidents, occupational hazards or suicide. Deaths due to CO poisoning were studied retrospectively in the period 2000-2018 at the Institute of Forensic Medicine, Timişoara, Romania. These cases represent 1.75% of all the autopsies and 0.63% of all violent deaths. There have been cases of single deaths and cases with multiple victims - concomitant deaths. The analysis of lethal CO intoxication cases that occurred in different circumstances (incomplete burning with CO accumulation, fires - associated with burns, death in the fountain - due to fossil fuel pump failure, suicide due to exhaust gases) was based on the examination of 298 autopsy files. In this type of poisoning, the forensic examination of the body is marked by the non-specific character of most of the macroscopic and microscopic changes. Although inconstant, these types of changes (e.g., red discoloration of livor mortis) raise the suspicion of death by CO poisoning; the essential contribution to establishing cause of death resides in the determination of carboxyhemoglobin (COHb) concentration by spectroscopy. In all cases, the cerebral and cardio-pulmonary modification and their contribution to the cause of death were studied. Co-morbidities interfere with the cause of death in cases with average COHb concentrations, in the 20-50% range, where CO blood levels alone are not reason enough to explain the onset of death.