Experimental testing of a volume index as a fast method for estimating carbon stock in the understorey vegetation. The biomass of understory vegetation has an important role in several forest ecosystem processes, though it is not frequently included in forest inventory programs, which are commonly focused on the tree component. The objective of the study is to test a fast procedure for obtaining an accurate estimation of three components of the aboveground understory vegetation: herbaceous, bush, regeneration. For such a purpose a Volume Index has been calculated on the basis of the product between the percent coverage of vegetation and the average height of the three different components of understory vegetation. The index has been quantified in twenty clusters of four squared plots 1 m2 wide; clusters were located in two study areas in the northern part of Molise Region (southeastern Italy). For each plot, the dry biomass has been collected and weighted, and then transformed in carbon stock. This study presents the field protocol and the achieved results in terms of measured aboveground understorey carbon stock in six different forest and pre-forest types (the average carbon stock was 1.19 t C ha-1) and correlation between Volume Index and carbon stock (the Pearson's correlation index was 0.8 on 309 field observations).