The study area is located in the south western Cameroon and includes part of the Cameroon Volcanic Line (CVL). Volcanic activity has been recorded in this area, precisely on the Mount Cameroon which recently erupted in 2002. In addition, deadly carbonic gas was emitted by crater lakes (Monoun and Nyos) in 1984 and 1986 respectively. Potential field model EGM2008 has been used to investigate the structure of the crust. A regional/residual separation is performed using upward continuation and polynomial separation methods. The results from this operation show a similarity between the regional anomalies resulting from both methods. The regional anomaly maps present an increasing gradient trending ENE-WSW above and below latitude 5˚N. Moreover, six nearly parallel profiles were drawn on the CVL in addition to two other profiles at the northern edge of Congo craton. These profiles were used to estimate the depths of the Moho discontinuity and some shallow sources by the means of the Bouguer and the residual anomalies respectively. The results show that the Moho discontinuity depths vary from 19-25 km (under Mount Cameroon) to 28-34 km (in Kumbo), while the southern neighbouring zone presents a Moho discontinuity depth ranging between 23-31 km (in Ngambe) and 22-32 km (in Eseka). These findings agree with the previous seismic and gravity researches lead in the area. EGM2008 is therefore a reliable tool to investigate the subsurface structures.