Objectives: The purpose of this study was to investigate the attainment of treatment goals according to the European Consensus Programme (ECP-TGs) from 2011 in patients with moderate to severe psoriasis (Pso) treated with the first conventional systemic therapy and to identify factors that might compromise the attainment of these treatment goals. Methods: In a multicenter, prospective observational study, patients with moderate to severe Pso, defined as either body surface area (BSA) >10% or psoriasis area severity index (PASI) >10 and dermatology life quality index (DLQI) >10, received a conventional systemic therapy that could be modified at each follow-up visit over the course of 18 months. All subjects signed an informed consent form, were ≥18 years of age as well as systemic therapy naïve, and had regular study visits at months 3, 6, 9, 12, and 18 after baseline. Among others and in addition to demographic and disease-related characteristics at baseline, we documented BSA, PASI, DLQI, and the physician-reported attainment of treatment goals at each follow-up visit. Factors related to a failure in achieving the ECP-TGs (i.e., either Δ PASI ≥75 or Δ PASI ≥50 and <75 with a DLQI ≤5) at month 18 were investigated by multiple logistic regression. Descriptive results are presented as the mean ± SD for interval data, and absolute as well as relative frequencies for nominal data. For this part of the analysis, data at baseline and months 6, 12, and 18 are presented. Results: A total of 133 Pso patients with a mean age and disease duration of 49.5 ± 14.4 and 15.6 ± 12.8 years, respectively, were included in the analysis; 54.1% (n = 72) were male. The mean baseline disease-related outcomes were: BSA: 21.5 ± 15.8%, PASI: 13.7 ± 7.14, and DLQI: 12.0 ± 6.11. The most common conventional systemic therapies initiated at baseline were fumaric acid esters (n = 74, 55.6%), methotrexate (n = 46, 34,6%), and ciclosporin (n = 6, 4.5%). The ECP-TGs were achieved by 58 patients (43.6%) at month 6, 86 patients (64.7%) at month 12, and 97 patients (72.9%) at month 18. An optimized reduced logistic regression model identified the presence of onycholysis/nail dystrophy at two or more digits to be associated with failing to attain the ECP-TGs (OR 10.7, 95% CI 2.5–46.7, p = 0.002). Conclusion: Patients with onycholysis/nail dystrophy at two or more digits were identified as having a higher risk of not achieving ECP-TGs under conventional systemic therapy. The ECP-TGs from 2011 were attained by 43.6% of our patients 6 months after starting conventional systemic therapies. In the era of safe, fast, and efficacious Pso therapies, much higher treatment goals might be achieved during therapy. New treatment goals are only of use if patients and dermatologists strive to attain them.