This study represents the first comprehensive investigation of two-pore domain (K2P) K+ ion channel expression within the mammalian retina. Our data indicate that mRNA transcripts for numerous K2P channels are detected in the mouse retina, including inwardly rectifying TWIK-type channels, acid sensitive TASK-type channels, arachidonic acid mechanosensitive TREK-type channels and calcium sensitive TRESK channels, with many K2P channel transcripts showing dynamic patterns of expression throughout the day and during postnatal development. Antibody labelling confirms the widespread expression of K2P channels in the mouse retina and indicates that the highest levels of K2P channel expression are observed in retinal ganglion cells and Müller cells. Overall, levels of K2P channel protein detected are broadly consistent with our mRNA studies in adult tissue and during postnatal development. Typically, channels showing high levels of mRNA expression resulted in high levels of convincing immunoreactivity (TWIK-1, TASK-1, TREK-1, TRAAK), whereas channels showing low levels of mRNA expression typically showed low or absent levels of protein expression (TASK-2). One notable exception was TRESK. Despite high levels of mRNA consistently detected by qPCR analysis (and by gene microarray analysis – Hughes et al., unpublished data) we detected only low levels of TRESK protein, with few cells convincingly labelled (including samples collected at various circadian time points). The reasons for this discrepancy are not clear, but likely reflect technical limitations of the antibody used.