一 . 如果后面接名词、代词或名词性词组时,两者基本上可通用.例如：
I doubt/suspect the truth of her statement. 我对她那番话的真实性表示怀疑.
He says he can cure me, but I still doubt/suspect him. 他说他能治好我的病,但我仍对他不放心.
二 . 如果后面接 that 从句,意思就截然不同. doubt 意为“无把握；不相信（ question the truth of； don't believe/think ）”,怀疑其无. suspect 意为“有存在或属实的想法；相信（ have an idea of the existence； believe； guess ）”,怀疑其有.例如：
I doubt that he has stolen my watch. 我不相信他偷了我的手表.
I suspect that he has stolen my watch. 我怀疑 / 猜想他偷了我的手表.
The doctor suspected that he was ill with flu. 医生怀疑 / 认为他得了流感.
这时 doubt 更多用于否定句或疑问句中.如：
I don't doubt that he is right. 我确信他是对的.
I didn't doubt that he would come. 我当时相信他会来的.
Why did she doubt that they were cheats? 她为什么怀疑他们是骗子?
三 . doubt 用于肯定句中时,多接 whether/if 引导的从句,意义与 that 从句不同,这时意为“不敢肯定（ feel uncertain about ）”.而 suspect 不可接这种从句.例如：
I doubt whether/if he'll come. 我不敢肯定他来不来.
It's raining hard. I doubt whether it will be fine tomorrow. 雨下得很大,我不敢说明天会晴.
四 . 其他搭配.
doubt 可作不及物动词,用于 doubt of sth； suspect 用于 suspect sth to be, suspect sb of（doing） sth .例如：
She never doubted of his success. 她从不怀疑他的成功.
I suspected him to be the spy. 我认为他就是那个间谋.
What made you suspect her of having taken the money? 你凭什么怀疑钱是她偷的