The purpose of the present study was to investigate the intra-observer and inter-observer reliability of three resonance frequency analysis (RFA) devices and to compare the implant stability quotient (ISQ) values according to implant macro design and diameter in two different bone densities. A total of 64 implants (Neoss Proactive) of varying diameters (3.5 and 4.0 mm) and implant macro design (tapered and straight) were placed in two artificial bone blocks (the density of type 2 and 3). The implant primary stability was measured using Osstell IDx, Osstell Beacon and Penguin RFA. The ISQ value of each implant was measured by two observers and recorded five times in two directions. The intra-observer and inter-observer reliability of RFA devices were evaluated. In addition to that, mean ISQ values were calculated for each RFA device to evaluate the effect of implant diameter, implant macro design, and bone density on ISQ values. ISQ values were significantly higher for implants placed within the type 2 bone than for the type 3 bone. The 4.0 mm diameter implants presented higher ISQ values than 3.5 mm diameter implants. The intra-class correlation coefficient (ICC) values for intra-observer reliability were above 0.85 for each observer and the ICC values for inter-observer reliability were 0.94, 0.93, 0.98 for Osstell IDx, Osstell Beacon and Penguin RFA, respectively. Although there was excellent inter-observer reliability with three RFA devices, the intra-observer reliability of Osstell Beacon and Penguin RFA were slightly better than Osstell IDx. Bone density and implant diameter were parameters affecting the primary stability of implants.