Objective: To investigate the fractal dimension (FD) and lacunarity of dentin in the presence or absence of a smear layer using scanning electron microscopy (SEM) images at various magnifications. Materials and Methods: Extracted human mandibular premolar teeth were divided into two groups (n=5). After decoronation, the root canals were prepared. While the smear layer was left intact in the first group, it was removed with 5% EDTA and 2.5% NaOCl irrigation in the second group. The roots were split longitudinally and one half was prepared for SEM. Four images at 500 and 1000 magnifications were obtained from the middle thirds of the root canals of each specimen and saved in TIF format. The FD and lacunarity of the SEM images were calculated. Two-way ANOVA and Bonferroni tests were used for statistical analysis (p=0.05). Results: The FD of dentin surfaces with or without a smear layer did not differ significantly (p>0.05). While magnification was an important factor in the FD of smear-free surfaces (p<0.01), it did not present any significant difference in the presence of a smear layer (p>0.05). Lacunarity showed a significant decrease in the images without a smear layer (p<0.0001). Although it demonstrated a slight increase with magnification, this increase was not significant (p>0.05). Conclusions: Lacunarity was a differentiating factor in determining the presence or absence of the smear layer regardless of the magnification of the SEM images. FD was affected by magnification and could not discriminate the presence or absence of the smear layer. Lacunarity analysis may be a practical tool for evaluating SEM images of dentinal surfaces.