Brain-Computer Interfaces (BCIs) enable users to interact with computers without any dedicated movement, bringing newhands-free interaction paradigms. In this paper we study the combination of BCI and Augmented Reality (AR). We first tested thefeasibility of using BCI in AR settings based on Optical See-Through Head-Mounted Displays (OST-HMDs). Experimental results showedthat a BCI and an OST-HMD equipment (EEG headset and Hololens in our case) are well compatible and that small movements of thehead can be tolerated when using the BCI. Second, we introduced a design space for command display strategies based on BCI in AR,when exploiting a famous brain pattern called Steady-State Visually Evoked Potential (SSVEP). Our design space relies on fivedimensions concerning the visual layout of the BCI menu ; namely: orientation, frame-of-reference, anchorage, size and explicitness. Weimplemented various BCI-based display strategies and tested them within the context of mobile robot control in AR. Our findings werefinally integrated within an operational prototype based on a real mobile robot that is controlled in AR using a BCI and a HoloLensheadset. Taken together our results (4 user studies) and our methodology could pave the way to future interaction schemes in AugmentedReality exploiting 3D User Interfaces based on brain activity and BCIs.