Secondary arterial hypertension is one of the major under-diagnosed and under-treated cardiovascular complications of sleep apnoea syndrome (SAS), in spite of its 40-70% prevalence in adults [1,2]. Ambulatory blood pressure monitoring (ABPM) can contribute very effectively to screening and treatment control of hypertension, by detecting about 1/3 of hypertonics not observed by standard BP meassurement [3,4]. BP parameters obtained by ABPM were correlated with indices measured during whole-night polysomnographic examination in 57 adults. The patients were divided into 4 groups: simple snoring (apnoea/hypopnoea index (AHI) 25/h, n=17) and a group of severe SAS treated with nasal continuous positive airway pressure (CPAP, n=12). The time of sleep with snoring correlated with nocturnal, morning, diurnal, average and minimum diastolic BPs (p<0.05, n=45, linear correlation) but not with SBP. Ventilatory parameters such as AHI, obstructive apnoea with bradycardia or oxygen desaturation, hypopnoea and oxygen desaturation index, correlated significantly (at least p<0.05) with an increase in diastolic BP values (nocturnal, diurnal and morning 2 h after awakening, which is the most likely time for strokes). The main parameters of oxyhaemoglobin saturation (such as minimal SatO₂, avgSatO₂ and O₂ saturation <85%), correlated negatively with practically all diastolic BP data, but only with some parameters of systolic BP. Particularly the morning values measured 2 h after awakening and the diurnal, nocturnal and minimal DBP data changed. CPAP therapy improved both the saturation and BP values by decreasing the number of apnoea/hypopnoea episodes, and eliminating the intermittent hypoxaemia and increased arousal reaction and sympatho-adrenergic hyperactivity. ABPM allows the selection of the most predictive BP parameters for large-scale screening of both hypertension and SAS, to reveal diastolic hypertension appearing in early phase of the disease and to manage an effective therapy also for drug-resistant hypertension by long-term use of CPAP treatment.