In tropical deciduous forests (TDF), the scaling relations between size attributes in columnar cacti vary across species, partially because of environmental pressures to reach the canopy. This study aims to compare the growth-related allometric relationships between Pilosocereus leucocephalus (Poselg.) Byles & G.D. Rowley and Cephalocereus scoparius (Poselg.) Britton & Rose, two conspicuous species of columnar cacti in the TDF of Mexico. Nonlinear regression models were used to estimate maximum height ( H max ) from diameter and Reduced Major Axis (RMA) regression models to relate crown cover a height and diameter. The scaling exponents in both species were similar to other pachycaulous plant species. However, despite a lower maximum height ( H max ) in the species P. leucocephalus, it has an allometric height exponent than that recorded in C. scoparius , which suggests that P. leucocephalus allocates more biomass to vertical development in the early stages of growth. Our results showed that the stems of C. scoparius increased in height at a far less rate concerning high than P. leucocephalus , demonstrating that cacti display different interspecific strategies to coexist in TDF. In contrast, greater height enables C. scoparius to reach the forest canopy and compete with C-3 tree species. The columnar cacti also differed in size and branch number through their development, thus representing two biomass allocation strategies to optimize light capture or cope with seasonal drought stress.