The scaling relationship of leaf dry mass (M) versus leaf area (A) is crucial for understanding the tradeoff between leaf construction cost and the photosynthetic area return across diverse environmental stresses. Because leaves at different spatial positions on a plant receive varying intensities of light, this can affect the overall assessment of leaf scaling; however, the impact has not been tested. We collected a total of 1,746 leaves from 217 Lamium barbatum plants and measured their M and A. These leaves were grouped based on vertical (upper layer and lower layer) and horizontal (east, south, west, and north) positions. Reduced major axis regression protocols were used to evaluate the scaling relationship between M and A, and the bootstrap percentile method was employed to determine the differences in scaling exponents across different positions. ANOVA with Tukey’s HSD test was utilized to compare the M, A, and leaf dry mass per unit area (LMA) across these spatial positions. The results showed that: (1) M, A, and LMA were not significantly different among horizontal positions; however, these traits in the lower layer leaves were significantly greater compared to the upper layer leaves; (2) The scaling exponents of M versus A were also not significantly different across horizontal positions, but the scaling exponents of the lower layer leaves were significantly smaller than those of the upper layer leaves. Although the leaf scaling of M versus A tends to be consistent horizontally, it is necessary to consider the impact of their longitudinal positions on biomass investment for the photosynthetic area when conducting experiments on leaves.