Phil Redman, research director for Gartner said, "When assessing the total costs of wireless mobile products, we found that the more capable the device, the higher the cost."
With a wireless modem, the annual cost to a business of a handheld computer rose by $1,392 (£953) to $4,392 (£3,005) per user.
Hardware, software and network services account for 60% of the costs. Some 30% is taken by operational costs, such as technical services and support, peer support, application management and development. A further 10% goes on administration, including evaluation, implementation and training.
The full findings will be discussed at Gartner's Mobile Business and Technology 2002 Conference, which takes place next week (17-18 June) in Denmark.
Redman advised businesses to take into account these management costs when evaluating whether handheld computers gave a good return on investment.
"Enterprises that link mobile technology investments to job functions and bottom-line productivity indicators, such as sales revenue, customer support and internal operations goals, will be successful at defining a mobile ROI," he said.
To reduce overall TCO when deploying handheld computers in a wireless LAN, Gartner advised users to consolidate network service providers, bundle services and aggressively negotiate contracts.