What's the difference between be careful about/of/with/in? Be careful ABOUT what you say to him . (regarding or concerning something) Be careful of him . He is a bad guy. / Be careful of people who want to cheat you Bec careful in choosing your friends ./ be careful in China . ok? The difference > you have to study these 3 word thoroughly to know their various usage . Try the Internet . Its too long to explain here , if I can )