The Taiwanese firm hopes to challenge the iPhone 4 with the large-screen Desire HD and the Desire Z with its fold-out keyboard.
Both HTC phones are based on Google's Android operating system.
They come a day after Finnish rival Nokia presented three phones to revive its flagging smartphone division.
Mobile phone makers and network operators are betting heavily that consumers are keen on a connected and multimedia experience on the move.
Smartphone sales soar
Speaking at the HTC launch, Patrick Chomet, global director of terminals at network operator Vodafone, said smartphone sales were soaring, already taking more than 30% of the market; in two years Vodafone expects that smartphones will make up 70% ot total mobile phone sales.
With most smartphones now easy to use, customers are making heavy use of new services. During the past year, Mr Chomet said, Vodafone had experienced a doubling of data traffic for both location services like maps, and access to social networks like Twitter and Facebook.
