Oxygen microopt(r)odes have recently been introduced as an alternative to microelectrodes in the field of aquatic biology. We here describe adaptation, test results and first in situ measurements made with O₂ microopt(r)odes on deep-sea benthic landers. This includes a detailed description of the sensors, the mechanical mounting, and the necessary measuring system. Hydrostatic pressure effects on the sensors and the optical penetrators are evaluated and discussed. Further, in situ micoopt(r)ode data obtained by a profiling lander (Profilur) and a benthic chamber lander (Elinor) are presented, discussed and compared to measurements obtained simultaneously by Clark type O₂ microelectrodes. The obtained data demonstrated that opt(r)odes are a realistic and good alternative to electrodes for landers and other measuring platforms during deep-sea deployments.