Introduction: Body weight dissatisfaction, when current and desired body mass index (BMI) do not align, is common in persons with obesity. The aim of this cross-sectional study was to explore factors associated with the differences between current and desired BMI, and ideal BMI (defined in the present study as BMI 25 kg/m<sup>2</sup>), in persons with obesity. Methods: Swedish citizens aged 20–64 years residing in the Stockholm County were randomly selected from the population register at five different and evenly separated occasions in the study period 1998–2000 and invited to provide self-reported data about their current weight, height, desired weight, and other characteristics such as depressive symptoms and alcohol intake. Among the 10,441 participants with a mean BMI of 24 kg/m<sup>2</sup>, differences between desired BMI and ideal BMI were calculated to determine the discrepancy between desired BMI and ideal BMI in participants with obesity (n = 808). The discrepancy between current and desired BMI was also determined. Using linear regression, factors associated with BMI discrepancies were determined. Results: Persons with BMI <40 kg/m<sup>2</sup> desired a lower BMI than those with BMI ≥40 kg/m<sup>2</sup> (26 ± 3 vs. 36 ± 14 kg/m<sup>2</sup>, p < 0.001). Women with obesity (n = 425) had a larger discrepancy between current and desired BMI, 32% ± 16, than men with obesity (n = 380), 24% ± 21 (p < 0.001). Persons with obesity and major depression had a 6.9% (95% CI: 2.5–11.4) larger discrepancy between current and desired BMI than persons with obesity but without major depression. Being born abroad, having a university degree, or hazardous alcohol use were not associated with discrepancy between current and desired BMI or desired BMI and ideal BMI (all p > 0.05). Conclusion: Desired BMI and discrepancies between current, desired, and ideal BMI vary according to current BMI, sex, and presence of major depression. This underscores the significance of a patient-centered approach in the management of obesity, where the goals and needs of each patient should be considered.