Multiple K⁺ channels are expressed in the respiratory epithelium lining airways and alveoli. Of the 3 main classes: (i) voltage-dependent or calcium-activated, 6-transmembrane domains (TMD), (ii) 2-pores 4-TMD, and (iii) inward-rectified 2-TMD K⁺ channels, almost 40 different transcripts have already been detected in the lung. The physiological and functional significance of this high molecular diversity of lung epithelial K⁺ channels is intriguing. As detailed in the present review, K⁺ channels are located at both the apical and basolateral membranes in the respiratory epithelium, where they mediate K⁺ currents of diverse electrophysiological and regulatory properties. The main recognized function of K⁺ channels is to control membrane potential and to maintain the driving force for transepithelial ion and liquid transport. In this manner, KvLQT1, KCa and K_ATP channels, for example, contribute to the control of airway and alveolar surface liquid composition and volume. K⁺ channel activation has thus been identified as a potential therapeutic strategy for the resolution of pathologies characterized by ion transport dysfunction. K⁺ channels are also involved in other key functions in lung physiology, such as oxygen-sensing, inflammatory responses and respiratory epithelia repair after injury. The purpose of this review is to summarize and discuss what is presently known about the molecular identity of lung K⁺ channels with emphasis on their role in lung epithelial physiology.