We recommend that you carry your passport (or, if a resident your Croatian ID card) at all times. They are the only officially recognised form of identification in Croatia.
Keep a photocopy of the biographical details page in a safe place, including details of your next of kin. If your passport is lost or stolen you should report it to the police and get a police report. You need to do this before applying for an Emergency Travel Document; advice on how to apply can be found here
Drug related offences are punished with fines and jail sentences.