Wispa Gold and Double Decker bars sold in multipacks will shrink in size.
The chocolate favourites are getting smaller so they contain less than 200 calories.
Cadbury has made the move in an attempt to help tackle obesity, with plans to reduce calories in all multipack chocolate bars to 200 calories or fewer by 2021.
However, the smaller chocolate bars will cost the same, reports The Guardian.
A Cadbury spokesperson told the publication: "The list price for these products will not be changing at this time. Retail pricing remains at the retailer’s sole discretion."
The news comes after Cadbury announced childhood favourites Fudge, Curly Wurly and Chomp were set for a calorie cut.
Currently there are 114 calories in a Fudge, 118 in a Curly Wurly and 110 in a Chomp.
However, the chocolate bars will be reduced to be below 100 calories "over the next few months".
The UK managing director at Mondelēz International, the US company that owns Cadbury, said: "We recognise we must play our part in tackling obesity and are committed to doing so without compromising on consumer choice."
Adding: "A focus on portion control is recognised as one of the most effective ways of helping people balance their calorie intake."
