The Siena was of the same generation as the Psion Series 3 but it has a smaller size liquid-crystal display (LCD, 240 x 160 pixels) and a separate numeric keypad next to the screen.

Although the Siena shares binary compatibility with the Series 3, many programs had to be modified due to the reduced sizes of memory and display.

That port also provides PC connectivity if used with the separately available PsiWin software and dial up access via the Travel modem accessory.

The device was used as a model for a gadget in Anarky (vol.1) #3, Metamorphosis: The Economics of The Madhouse, a DC Comics book.

The character, Anarky, is seen tracking Batman's movements using the small PDA.