Hieni, I own a pair, and they fit true to size on me.
Mine are in a size 38, and I'm normally between 37.5-38 depending on the designer. If you have narrow feet, you should be able to go with your usual size; Otherwise, I suggest going 1/2 size up.
The best thing is to try them on in person though :)
Also.. I love them! They're not the most comfortable flats (you need to break them in), but they're just too cute. I think you should definitely get them!! I'm considering getting the latest version - the sketched mouse.
I love my miu miu flats. They're really comfortable, and go with almost anything.
i was told to go a half size even a size up by a friend who had them. however,she said it wasnt comfy at all. it bit into her back heel. so it put me off buying a pair. however, i bought the jelly flats instead. and they're SOOO comfy..!! they run true to size and i've worn them everywhere possible.