This chapter delves into the impact of robot personality. The first half focuses on designing a robotic system to offer adaptive assistance based on its personality traits, which are determined from data collected from human-human interactions on the same task. The results from a study with \(N=24\) participants show promising evidence for the effectiveness of modelling robot personality traits and highlight the influence of the similarity/complementarity principle in human-robot interaction scenarios. The second half investigates the impact of personality-driven behavioural patterns, modelled in terms of communication styles, on users’ intention to use the robot. Two robots are designed: one with an introverted, empathetic style and the other with an extroverted, provocative style. They are then evaluated in a real-world scenario with \(N=209\) untrained participants. The findings indicate that the robot’s communication style affects user acceptance, with the provocative robot being perceived as more useful and the empathetic robot as more enjoyable. These results underscore the significance of communication style in influencing users’ acceptance.