Shoppers can sign up for AOL Broadband and buy an Easy-Install modem pack in the stores across the UK.
Comet is promoting and distributing AOL Broadband in its 260 UK stores.
In-store activity includes display units containing AOL Broadband Easy-Install modem packs and AOL Broadband booklets on counters. This is supported by above-the-line joint marketing activity.
AOL Broadband is also available in a selection of Carphone Warehouse stores, with a planned nationwide roll-out.
Stores will promote the benefits of AOL Broadband via in-store material such as posters, Easy-Install modem packs and AOL Broadband booklets.
Both deals come as extensions of existing agreements for the distribution of AOL's narrowband service.
Karen Thomson, chief executive of AOL UK, said: "Our aim is to make it as easy and stress-free as possible for consumers to sign up for broadband.
"AOL already offers telephone and online registration; these stores will give consumers the opportunity to learn more about broadband."
Bill Moir, computing category manager at Comet, said: "We have a very successful relationship with AOL, so we were keen to extend this to broadband. We always seek to offer good value and high-quality services to underpin our computing offering."