當(dāng)表示“至于”這個意思時，as for，as to都可以用，一般位于句首，但as for常含有貶義；當(dāng)表示“關(guān)于”，后跟whether、when、what、where、how等引導(dǎo)的從句時，只能用as to，有時as to可省略。這種用法上的as to一般位于句中。

1、as for在語體上不如as to 正式，并且著重話題的轉(zhuǎn)換，也就是說，它所引導(dǎo)的是前面尚未提到過的新的事情，因此，它不能用于文章的開頭。

例句：As to that, I haven’t decided yet.此時用于句首，不能用as for。關(guān)于那件事，我尚未做出決定。

2、as to常常與wh-疑問詞引導(dǎo)的動詞不定式和名詞從句連用（有時可省略），而as for卻沒有此種用法：

例句：Nobody could decide as to)what to do.誰也不能決定該做什么。

as for意為至于，就…方面說來。引導(dǎo)時間狀語從句。主句可以是主動句，也可以是被動句。

例句：As for avoiding you, nothing could be further from my mind.

至于說躲避你，我根本就沒有這樣的想法。

As for his job — well, he was very mysterious about it.

至于他的工作，他總是顯得非常神秘，從不多說。

As for doctors, when you go to see them they just look right through you.

說到醫(yī)生，你去看病時，他們直把你當(dāng)透明的。

As for anything told to me in confidence, well, my lips are sealed.

至于私底下告訴我的任何事情，我會守口如瓶的。

As for Laura and me, the colour of our skin has never mattered

至于我和勞拉，膚色根本不是問題。

As for her engagement with Adam, I would say the portents are gloomy.

至于她和亞當(dāng)?shù)幕榧s，我看兆頭不妙。

As for the present, things are far better than at any time in the past.

如今呢，可比以往任何時候都要強。