This chapter is part of the book “EEG/ERP Analysis: Methods and Applications” and it attempts to give different examples of applications of quantitative EEG (qEEG) for the realization of brain-computer interfaces (BCIs). In particular, we think that neurotechnologies for BCIs based on electroencephalography (EEG) offer advanced tools of interest for other research and application fields. EEG-BCI technologies are based on the electrical nature of brain activity. EEG-BCI captures the user state or intent via electrical signals recorded on the scalp and maps them into computer or device commands. As the reader can imagine, such a process goes through an intermediate process of quantification. We explain some of these techniques in the following chapter.