<b><i>Background:</i></b> Patch or plaque stages in mycosis fungoides (MF) have different prognoses. The recent staging system proposed for MF discriminates between patches and plaques based upon clinical features. <b><i>Objective:</i></b> To estimate interdermatologist agreement on the morphological evaluation of MF lesions. <b><i>Methods:</i></b> Twenty-four patients with MF were enrolled. Two dermatologists evaluated every lesion face to face and independently with respect to the patch-plaque status. Cohen's κ was used to determine the rate of agreement. <b><i>Results:</i></b> Agreement was 67% with respect to the patch or plaque status [95% confidence interval (CI) = 49-85%; p < 0.001]. Current systemic treatment (56%; p = 0.01) was associated with lower agreement. Younger age at diagnosis [odds ratio (OR) 1.03 (95% CI 1.02-1.05)], younger age at enrolment [OR 1.03 (95% CI 1.02-1.04)] and time on systemic treatment [OR 1.02 (95% CI 1.01-1.04)] were independent risk factors for disagreement (p < 0.001). <b><i>Conclusion:</i></b> The new system for MF staging carries a significant risk of disagreement regarding patch and plaque subsets.