Success of advanced cardiac life support (ACLS) depends on several factors: character and severity of the primary insult, time interval between cardiac arrest and effective basic life support (BLS) and the ensuing ACLS, patient's general condition before the insult, environmental circumstances and efficacy of BLS and ACLS. From these factors, only the efficacy of ACLS is under control of emergency personnel. The end tidal partial pressure of CO2 (P(ET)CO2) has been shown to be an indicator of the efficiency of ACLS and a general prognostic marker. In this study P(ET)CO2 was monitored during out-of hospital ACLS in three cases of cardiac arrest of different aetiology. The aetiology included lung oedema, tension pneumothorax and high voltage electric injury. P(ET)CO2 served for adjustments of ACLS. In these three cases the predictive value of P(ET)CO2 monitoring corresponded to previously reported recommendations.