Canarywood is correct, there are numerous species of cedar, and many different grades within each species. Some species of cedar are totally unsuitable for decking, other species will work if they are top grade, and other species can work even if they are not top grade. Best to discuss the project with a KNOWLEDGEABLE lumberyard, certainly not a big box store.
Note that cedar is typically rather soft, easily scratched, and is generally a relatively weak wood, meaning you will likely need 2x stock for the deck. An alternative wood is ipe, a South American hardwood that is very strong, very hard, and very resistant to rot. Also can be very expensive, depends on where you live. My deck is ipe, a good choice for longevity and does not require any maintenance, but is more difficult to install than PT or cedar because it is very hard.