Introduction. Implant-prosthetic rehabilitation is popular and fast growing treatment care opportunity with development of new products and techniques. This offers a new possibility for patients with completely edentulous jaws to get rid of complete dentures. However, the lack of a well-defined and prosthetically driven approach may result in total failure of rehabilitation procedure.  Aim of the study. To highlight the main prosthetic element of full mouth rehabilitation on implants.  Materials and methods. The paper is based on analysis of medical literature and treatment of 35 patients (aged between 32 and 73 years old) with full edentulous upper and/or lower jaws using implant-supported prosthesis (39 prostheses). The patients were mainly rehabilitated with tilted implants according to all-on-4 protocol. The treatment time was divided in two parts, provisional treatment, and final one. The first one had a 6-12 months period. After treatment, seven elements have been identified as key factors in prosthetic planning of full edentulous cases whose ignorance can lead to complete failure of aesthetical and functional aspects.  Results. To have predictable and functional results, the patients must be investigated by the prosthodontist to identify their needs and expectancies. The key indicative factors are position of incisal edge of upper frontal incisors, restorative space, lip support, smile line and lip length, contour and profile emergence, contact with soft tissues, and occlusal scheme.  Conclusions. The prosthetic planning of complex cases in full mouth rehabilitation is essential for aligning the treatment plan along with patient’s expectations. By missing out the key planning factors, unpredictable and unfavorable results for both the doctor and patient could occur.