MD 108 serves as the northern edge of Columbia and connects several of the planned community's suburban villages.

The highway heads southeast and meets the southern end of Annapolis Rock Road, which leads to MD 94 at the Montgomery–Howard county line.

The highway passes a pair of gold courses and the historic home Oaks II.

The route continues southeast to the eastern edge of Olney, where the highway crosses James Creek and meets the northern end of MD 182 (Dr. Bird Road) next to Our Lady of Good Counsel High School and the Olney Theatre Center for the Arts.

The highway gains a center left-turn lane and passes Sherwood High School before intersecting MD 650 (New Hampshire Avenue) in the village of Ashton.

MD 108 gains a center left-turn lane as it begins to pass along the northern edge of the large, planned community of Columbia.

MD 108 continues east along the northern edge of the villages of Harper's Choice and Wilde Lake; between the two, the route passes historic Clark's Elioak Farm.

[1][2] MD 108 expands to a four-lane divided highway south of Lake Centennial and just west of its crossing of the Little Patuxent River in the village of Dorsey's Search.

The route meets US 29 (Columbia Pike) at a cloverleaf interchange and curves southeast as Old Annapolis Road, passing northeast of a park and ride lot.

MD 108 reduces to two lanes and passes along the northern edge of the Oakland Mills village.

The state highway continues south along the eastern edge of the village of Long Reach.

[18][17] Three segments of macadam road were constructed along Clarksville Pike from Olney through Sandy Spring and Ashton to Snell's Bridge between 1916 and 1919.

[20] Old Annapolis Road from Columbia to Jonestown was brought into the state highway system as MD 539 in 1956.

[26] MD 108 was expanded to a four-lane divided highway on either side of US 29 in conjunction with the construction of the interchange in 1987 and 1988.

[29][31] MD 108 was later widened at its intersection at Centennial Lane and Beaverbrook Road from the middle of 2021 to early 2023.