The purpose of this research is the creation of the framework for immersive Virtual Worlds (VW) development and evaluation of factors affecting user’s immersion experience in 3D virtual worlds. Three experiments have been conducted to evaluate different aspects of the immersion experience in virtual reality. The first experiment aimed to explore the influence of communication on users whilst performing certain activities in a virtual world. The second experiment evaluated how the real-world environment affects users in a virtual world. The third experiment examined the aspect of mobility as a main contributor to a user’s distraction. The fourth experiment partly confirmed previous findings and added new factors, affecting immersion experience. The results of all experiments formed a framework, containing factors which users considered as affecting them during their activities in virtual worlds. During the experimentation phase of this research a combination of qualitative and quantitative methods was used. The Grounded Theory (GT) methodology was applied for data analysis in qualitative part. The major contribution of this research is the framework of factors for building immersive 3D virtual environments. Another contribution is the evaluation of factors affecting users in such an environment.