Purpose: To evaluate the efficacy of short (5 or 6 mm-long) dental implants versus 10 mm or longer implants placed in crestally-lifted sinuses. Materials and methods: Twenty partially edentulous patients having 5 to 7 mm of residual crestal height and at least 7 mm thickness below the maxillary sinuses as measured on computerised tomography scans were randomised according to a parallel group design to receive either one to two 5 or 6 mm-long implants (10 patients) or 10 mm-long implants (10 patients) after crestal sinus lifting and grafting with anorganic bovine bone (Endobon). Implants were left to heal submerged for 4 months and loaded with reinforced acrylic provisional prostheses, and then replaced after 4 months, by definitive provisionally cemented or screw-retained metal-ceramic or metal-resin prostheses. Outcome measures were prosthesis and implant failures, any complications, radiographic peri-implant marginal bone level changes and patient's satisfaction assessed by blinded assessors, when possible. All patients were followed up to 1 year after loading. Results: No patient dropped out, no failures or complications occurred. Short implants lost 0.70 ± 0.19 mm of peri-implant marginal bone and long implants lost 0.87 ± 0.21 mm of periimplant marginal bone 1 year after loading, the difference between the two groups showing no statistical significance (difference = -0.17 mm; 95% CI: -0.35 to 0.02; P = 0.078). Conclusions: Both techniques achieved excellent results and no differences were observed between prostheses supported by one to two implants, 5 to 6 mm-long or 10 mm-long in the posterior atrophic maxillae up to 1-year after loading, therefore it is up to the clinicians to decide which procedure to use, although longer follow-ups are needed to understand if one of these procedures could be more effective in the long-term. Keywords: atrophic maxilla, short dental implants, sinus lift