The answer is YES if you use a train to or from Brussels International Airport (also called Zaventem Airport)
Diabolo Fee, also known as Brussels Airport Supplement, is a special airport tax for Brussels International Airport. Charging Diabolo fee on airport users started from 2012 to improve the accessibility of Brussels Airport from other locations in Belgium.
For example, if you move from Brussels International Airport to any main Brussels stations (Brussels North, Brussels Central and Brussels South) by train, Diabolo fee (€6.40 one way) is already included in your standard ticket price (€10.30 one way).
Everyone, include international travelers, over 12 years old must pay the Diabolo fee. Children under 12 years old and accompanied by an adult do not pay the fee.
Pay Diabolo Fee separately
Discount tickets and passes does not include Diabolo fee. If you already have one of the following tickets and passes, you will have to pay Diabolo fee separately.
Duo Ticket, Youth Holidays, Passes (Youth Multi, Standard Multi, Local Multi, etc), Eurostar ticket with “Any Belgian station” surcharge