The present invention refers to a process for preparing granules or particles comprising afatinib dimaleate, comprising the steps of providing afatinib dimaleate and at least one pharmaceutically acceptable excipient, and preparing granules or particles involving the use of at least one solvent selected from organic solvent and water, wherein all pharmaceutically acceptable excipients used in the process for preparing granules or particles have neutral or acidic properties, and wherein afatinib dimaleate has a solubility of at least 5 mg/ml in said at least one solvent. The present invention further refers to granules or particles comprising afatinib dimaleate that are prepared according to this process. Additionally, the present invention refers to a process for preparing a pharmaceutical composition comprising afatinib dimaleate, as well as to an adsorbate comprising afatinib dimaleate. Finally, the present invention refers to a pharmaceutical composition comprising afatinib dimaleate for use in a method of treating certain diseases.