You need installed the analytical accounts. You check Analytic accounting in menu Settings/Invoicing. In next step:

1. Menu Accounting/Chart of Analytic Accounts

2. Reporting/Analytic Entries Analysis

3. Accounting/Generic Reporting/Analytic

@zbik: I installed the analytics accounts, but I could not find where to generate the report?

When I go to Reporting/Analytic Entries Anlysis, I can see the "cost" by project, but not the "profit".

Any suggestions?

Thanks for your help!