According to Official Guinness Records,
The smallest modelling dog is 4 year old Bebe (USA), a long haired chihuahua who measures 17.14 cm (6.75 in) tall, 24.13 cm (9.5 in) long, and has worked for many companies in a paid capacity. Bebe is owned by Nikki Figular from Hamilton, New jersey, USA.
Bebe has also modelled for a number of websites and publications and has also made TV appearances as a canine model.
For a complete list of 2012 records, please visit 2012 Guinness Records in United States.