Strictly speaking, no, you cannot create another email address — with its own inbox — that's tied to your current Yahoo! ID. However, if you must have another email address that's separate from your default email inbox, there is a workaround. You'll have to create an email address, invite yourself to use the new address, then sign up for a new Yahoo! ID to associate with this address. How it works:
Visit the Email Control Panel, and click "Add an Email User."

Enter the email address you'd like in the text field under "Email Address."

Click "Next."
Now you'll decide how you'll access email. If you want to use Yahoo! to manage the address, click the first radio button; you'll have to register for a new Yahoo! ID to activate the address.

If you plan to use only POP to access this new email, you can select the second option; you won't need a new Yahoo! ID to activate the address. However, POP-only email addresses do not get our SpamGuard Plus feature, which helps protect you from spam.

When you're ready, click "Next."
On the invitation page, enter your email address to send yourself the invitation.

If you'd prefer, you can print the invitation by clicking the "View and print the invitation" link. A printer-friendly view of the invitation opens in a new window.

Click "Next."
On the confirmation page, click "Finish."
To start using the email address, you'll need to activate it. Note that adding yourself as an email user creates an email address separate from your current email account.
Tip: If you'd rather receive all your mail in one inbox, create an alias; messages sent to this address will be delivered to your primary inbox.