Electrical impedance tomography for the first time provides a bedside method for the non-invasive, reliable determination of regional lung function without radiation exposure. In contrast to other medical im¬aging methods, EIT displays body functions instead of body structures. The real-time images as well as the EIT-based special lung function pa¬rameters support clinicians with the regular evaluation of the variable pulmonary status in order to adjust the ventilation to individual patient needs. This, in turn, supports the implementation of lung-protective ventilation, therapeutic positioning, and weaning. This booklet was written to help you, dear readers, with the interpre¬tation of complex EIT data. Using simple decision flowcharts, the de¬scription guides the reader gradually and understandably through the assessment of functional imaging, while discussing possible causes for the respective findings and appropriate therapeutic measures. A variety of illustrations and supplementary information were added to further enhance understanding.