The companies have formed an alliance that will look at ad formats and ad serving models, as well as develop a system for getting customers to agree to receiving the ads.
Blake Chandlee, the director of UK media sales at Yahoo! UK & Ireland, revealed that ad agencies would be part of the process.
Options being considered include giving Vodafone customers discounts on phone bills if they agree to accept targeted ad campaigns.
The taskforce will also look at issues such as if it would be acceptable for users and advertisers to run video advertising, similar to that shown on TV, within video content.
Chandlee said: "When it comes to advertising on mobile phones, everyone knows it's going on, but no-one has put a flag in the ground. The objective is to learn together."
More people are starting to access the internet via mobile devices, and Yahoo! sees this as a trend that will continue globally. In some emerging markets, people are more likely to go on the web via phones than PCs.
Consumers using the Vodafone Live! mobile web portal are likely to see some form of display advertising, which begins in the first half of 2007.
Nick Read, the chief executive of Vodafone UK, said the alliance with Yahoo! would determine how best to give a richer mobile experience and create a compelling proposition for advertisers.