Atopic dermatitis is a chronic skin disease affecting quality of life, sleep, and mental health. Traditional evaluation methods focus on clinical assessments, but there is a growing need for tools that incorporate patient-reported outcomes (PROs). To evaluate the effectiveness of the Atopic Dermatitis Control Tool (ADCT) in assessing disease severity in patients with moderate to severe atopic dermatitis and to compare the efficacy of systemic immunosuppressants and dupilumab in patients with moderate to severe atopic dermatitis. A prospective, observational study was conducted across seven centres in Korea, involving 112 patients with moderate to severe atopic dermatitis. The ADCT, Eczema Area and Severity Index (EASI), and Dermatology Life Quality Index (DLQI) were used for assessing atopic dermatitis severity. In addition, the study assessed the effectiveness of immunosuppressants and dupilumab over the course of one year. The study found significant correlations between ADCT scores and other severity measures (EASI, DLQI). The correlation coefficients were 0.54 (p < 0.0001) for ADCT vs EASI and 0.83 (p < 0.0001) for ADCT vs DLQI. Furthermore, patients treated with dupilumab exhibited greater improvement compared with those on cyclosporine, as measured by the ADCT (adjusted OR [95% CI]); 6.98 [2.49, 19.58]). The ADCT effectively captures subjective aspects compared with the EASI and can be used practically and effectively in clinical settings of atopic dermatitis.