Yahoo! has many users worldwide, and due to the popularity of certain aliases, similar subscriber IDs are occasionally created. If you feel that a user is impersonating you, please cite specific examples where the user makes representations that s/he is actually you. With this information, we will be able to investigate the situation further and take the appropriate action as determined by our Terms of Service.

Yahoo! Mail
When that person is using Yahoo! Mail: If you believe someone is trying to assume your identity or misrepresenting themselves as you in an email sent via Yahoo! Mail, please send a detailed report describing the incident via our abuse feedback form.

Yahoo! Profiles or any other Yahoo! service
When that person is using Yahoo! Profiles, Personals or any other Yahoo! service: Please use our reporting form.