The cost of treating cutaneous T-cell lymphoma (CTCL) in Spain is unknown. With the advent of new treatments, it is more important than ever to gain an accurate picture of the true costs involved. The MICADOS study had 2 primary objectives: 1)to evaluate the impact of CTCL on patient quality of life, and 2)to evaluate the costs associated with the disease. This article reports the results of the cost analysis. We estimated the cost of treating CTCL over a period of 1year from the perspective of the Spanish National Health System. Twenty-three dermatologists and hematologists from 15 public hospitals analyzed data for adult patients with mycosis fungoides (MF) or Sézary syndrome (SS). A total of 141 patients (57.4% male) with a mean age of 63.6 years (95%CI: 61.4-65.7 years) were included. The mean direct annual cost of treating CTCL was €34,214 per patient. The corresponding costs by stage were €11,952.47 for stageI disease, €23,506.21 for stageII disease, €38,771.81 for stageIII disease, and €72,748.84 for stageIV disease. The total direct annual cost of treating MF/SS in public hospitals in Spain was estimated at €78,301,171; stageI disease accounted for 81% of all costs, stageII for 7%, and stagesIII andIV for 6% each. The MICADOS study offers an accurate picture of the direct cost of treating CTCL in patients with MF/SS in Spain and shows that costs vary significantly according to disease stage. Patient-borne and indirect costs should be analyzed in future studies.