This paper investigates how artificial intelligence (AI) is being adopted in higher education, combining theoretical and empirical perspectives. Building on established models of technology adoption, the study examines AI integration as a sociotechnical process shaped by cognitive, cultural, and institutional factors. An exploratory survey of 140 students, lecturers, researchers, and administrators across Lithuania, Portugal, and Greece identifies which AI tools are currently used in higher education settings, for what purposes, and with what perceived benefits and concerns. Results show widespread uptake of chatbots and translation systems for research, writing, and pedagogical support, alongside persistent concerns about accuracy, transparency, and academic integrity. The paper contributes a cross-national, multi-stakeholder account of AI adoption in higher education and highlights implications for institutional policy, tool design, and digital literacy initiatives that support both innovation and responsible use.