How much space do you have right now? If it's a mountain bike, you might be able to replace your 26" wheels with 700c wheels, but otherwise, I doubt it.
A 26" is ISO 559 mm whereas a 700c wheel is ISO 622 mm. If you want to use 700x28 tires, it means you need clearance for a radius of (622 mm / 2) + 28 mm = 339 mm... which is equivalent to the overall radius that you would get with 60 mm tires on ISO 559 wheels.
And it would look strange : lots of space on each side of the fork and stays, and barely a mm on the top.