serious attention
serious consideration
serious thought

But little serious thought has been given to this problem.

We'll give it some serious thought and let you know.

I want you to give some serious thought to this.

I'm going to have to give the problem some serious thought.

Perhaps it was time to give some serious thought to moving on.

I think you will give it serious thought and so avoid coming to a wrong decision.

Have you given serious thought to what these steps mean?

I think that this is something we have got to give very serious thought to.

So I gave some serious thought to what was important to me.

I'll give some serious thought as to what I want to do with the rest of my life.