Yes, you can travel to Spain with Diazepam (Valium), but because it is a controlled substance (a benzodiazepine), you must follow strict medical and legal protocols. You should carry the medication in its original pharmacy packaging with the prescription label clearly visible, and you must bring a letter from your doctor stating that the medication is for your personal use, the dosage, and the condition it treats. For short trips, a copy of your paper or digital prescription is usually sufficient, but for stays exceeding 30 days, you might technically need a "Schengen Certificate" or prior authorization from the Spanish Consulate. It is also important to carry only the amount necessary for the duration of your trip. Spain has a robust health system, and while Diazepam is available, it is strictly regulated; carrying it without proper documentation could lead to confiscation at customs or legal questioning. Always check the latest requirements from the Spanish Embassy if you are carrying a large supply.