what are the risk of hiring Non IT project manager on IT project manager job?

Mounir,

As I said my comment is based entirely on my experience and I have reservations on generalizing my own experience.

However I have looked at job openings for IT project managers and for most of them the prior experience working in IT but in a position other than project manager was not appreciated too much.

In many companies you can't get an IT project manager job if you don't have project management experience. The best way to gain project management experience is to start working on an entry level project management position such as project coordinator or junior project manager.

If you have served as a technical lead in several projects but the company you are working in has dedicated employees for managing projects then your chances to actually become a project manager are virtually non-existent. The only chance is to accept a much lower salary to start at an entry level position and then in a couple of years maybe you can get you old salary back.

These dedicated project managers however don't actually lead the teams in the traditional sense (giving instructions or orders) but instead ,as Sergio said, they engage the stakeholders.

While it is true that project managers could change industry it is also true that project managers who are not also subject matter experts will face a set of limitations while they are doing their work.

For instance the most important decisions that directly affect the team members are technical in nature. Team member don't care too much about project management related issues such as managing scope, stakeholders, budget and risk but all they care about is the technical approach to use in order to build the products or the services that have to be delivered.

A project manager who is not also a subject matter expert will virtually be excluded from the decision process used by the team members to build the products. The project manager can only check that the team members do understand what needs to be delivered and that they have an idea on what needs to be done. The project manager however does not have the capacity to tell whether or not the actions that the team members are about to perform will actually bring the project to success.

Non technical project managers are basically forced to blindly trust their team members on all technical issues and they have very little control in this matter. If the team members end up being slowed down or stopped by purely technical difficulties then the project manager will not be able to do much to help.

Non technical project managers also can't use a more directive leadership style when one is needed as they lack the capacity to formulate the instructions or orders to be given to the team members.