Which? a consumer group conducted a test and found that some coffees contain almost 400 calories.
The researchers said that lashings of full-fat milk, cream and chocolate are the causes with a skimmed milk cappuccino weighing in at fewer than 30 calories.
After testing products from three leading chains, the group also found that a burger would be a healthier option than some coffee house snacks.
The study found that one mocha coffee made with full-fat milk added up to 396 calories, and the same coffee with semi-skimmed milk, but topped with whipped cream, contained 326.
The difference between the shops was remarkable, with the full-fat mocha, cream and chocolate flake from the third branch having less than 300 calories.
It was also found that black coffee, which contains virtually no calories, had 17 when tested at one shop by an 'Americano'.
However, Which? said that even plumping for skimmed milk makes a huge difference.
When one skimmed milk cafe latte was tested, it was found that it contained 71 calories, while a 'skinny' cappuccino, with more froth and less milk, had only 27 calories.
The findings also showed that sandwich and cake counters in coffee shops were not the refuge of the healthy eater, either.
The research also found that while rich chocolate cake slices contained more than 600 calories each, even less obviously rich food would add to the fat if eaten regularly.
While one 'fruity flapjack' had a calorie-count of 423, a cheese and pickle sandwich in another chain topped 500 calories.
"You might be surprised to know that some coffee shop sandwiches contain more calories, fat and salt than a McDonald's Big Mac," BBC quoted the reports, as stating.
"Most of the big chains do have information about the nutritional value of their products on their websites," a spokesperson for Which? said.
"But we'd like to see this displayed prominently in their shops, so that customers can see how many calories are in their products," the spokesperson added.