Benjamin Blankertz Technische Universität Berlin In attention-based Brain-Computer Interfaces (BCIs), stimuli that are coupled to certain control actions (e.g., seletion of a symbol) have to be presented to the user in an efficient way. For paralyzed patients, the mode of presentation is crucial, as it must account for, e.g., impairments of the oculomotor system. In this talk, I will cover several aspects in the design of BCI driven spellers, in particular a novel approach that combines different sensory modalities. Furthermore, a recent development in monitoring hidden cognitive states will be presented.