According to Hoyme et al classification of hemihyperplasia, Hemifacial hyperplasia involves:
Hoyme et al (1998) provided an anatomic classification of hemihyperplasia: 

Complex hemihyperplasia is the involvement of half of the body (at least one arm and one leg); affected parts may be contralateral or ipsilateral.
Simple hemihyperplasia is the involvement of a single limb.
Hemifacial hyperplasia is the involvement of one side of the face.

Ref: Shafer's textbook of oral pathology 7th edition page 14
Half the body
Single limb
One side of face
None