The diagnostic efficiency of the methods of separate and combined registration of oronasal airflow and pulse oximetry in order to identify the obstructive sleep apnea/hypopnea syndrome (OSAHS) is studied in this work. Patients with cardiovascular diseases with complaints on sleep disorders were included in the study. Combined registration of oronasal airflow and pulse oximetry during sleep were performed for all examined patients (diagnostic system ApneaLink with pulse oximetry, ResMed). Registration results of oronasal airflow and pulse oximetry were analyzed separately and together. Apnea/hypopnea index (classic, recommended), desaturation index with a threshold of desaturation of 4% and 3% were evaluated as the diagnostic criteria for the identification of OSAHS. Also, in this paper the "apnea/hypopnea combined index" summarizing hypopnea episodes, which are associated with significant desaturation and without desaturation, was tested. As a method of comparison, polysomnography (Embla N7000, MedCare Flaga), which was carried out simultaneously with the main study, was used. The diagnostic efficiency of test methods and their criteria assessed by ROC-analysis (receiver operator characteristic, the characteristic curve analysis). The results of the study showed that combined registration of respiratory oronasal airflow and pulse oximetry during sleep was most effectively identified OSAHS and can be used as a screening method. The most accurate diagnostic criterion for identification of OSAHS is an "apnea/hypopnea combined index".