What are differences of public relations in public and private sectors?

Answer 1

There is no difference. The goals of PR are the same, only the messages produced are distinct. (Government needs to keep an image of eficiency while spending less; businesses need to project an image of profitability while cutting fat --e.g. workers).

The goals of PR (to support this "image") are the same in both public and private practice. It is only the messages (profit vs. common good; efficiency vs. profitability) that change.

Answer 2

There is actually little difference in public relations for public or private sectors.

The government uses PR firms to help them spin things properly, and big business uses PR firms, usually the same ones to boost them up.