Upper airway dryness is a frequent side-effect of nasal continuous positive airway pressure (nCPAP) therapy in obstructive sleep apnoea (OSA). In this situation, heated humidification is often used. Alternatively, oily nose drops are frequently applied to relieve dryness. The present study aimed to investigate the efficacy of a heated humidifier in comparison with oily nose drops. Twenty-four OSA patients complaining of serious nCPAP-related upper airway dryness were randomized to 6 weeks of treatment either with heated humidification (HC 100, Fischer & Paykel, Inc., Auckland, New Zealand) or oily nose drops (Colda-Stop, Desitin, Inc., Germany). The patients completed questionnaires on the degree and frequency of upper airway dryness, compliance with nCPAP, intention to terminate nCPAP and comfort during the nCPAP therapy. All 12 patients treated with heated humidification improved in terms of the degree and frequency of upper airway dryness, and reported greater comfort when using the nCPAP device. All patients in the heated humidification group intending to terminate nCPAP therapy because of upper airway dryness persisted with nCPAP on addition of humidification. In contrast, only five out of 12 patients (42%) in the oily nose drops group reported their degree of upper airway dryness to be improved (P = 0.003), only three patients (25%) reported an improvement in the frequency of upper airway dryness (P < 0.001), and only five patients (42%) reported greater comfort when using the nCPAP device with oily nose drops (P < 0.001). In the group using oily nose drops none of the three patients who intended to terminate nCPAP therapy persisted with nCPAP. Heated humidification is highly effective and superior to oily nose drops in reducing the symptoms of upper airway dryness during nCPAP.