Is my LAN susceptible to attack from my WLAN?

[fireking300]

Hello, like this title says I was wondering if my LAN traffic is able to be sniffed in the following cases.
Modem -> Switch -> Wireless router
-> LAN Router.

and this case

Modem -> Switch -> Wireless/LAN Router.

Any information would be very helpful.
P.S. My google searching skills are horrible but I did try searching but everything that turned up was about how to secure the wireless router.

Thanks.

[purehate]

This forum is for backtrack specific questions, if you are looking for general security stuff there are tons of other forums on the internet dealing with this subject.