The resistivity, ρ, of the spin-ladder compound CaCu₂O ₃ is investigated between T∼130-450 K. The ρ(T) data measured for (along the Cu-O-Cu leg) and (along the Cu-O-Cu rungs), ρ _a(T)>ρ_b(T), exhibit an activated dependence, similar in both directions and characterized by a nearest-neighbour hopping followed by a variable-range hopping (VRH) regime when T is decreased. A detailed analysis of ρ(T) demonstrates that conventional d-dimensional models of the hopping conductivity, based on the electron localization in disordered systems, cannot interpret the experimental data at any d ≤ 1, 2 or 3, leading to the mismatch of the characteristic energies and/or unphysical values of the characteristic length scales. The observed VRH conductivity law on the low-temperature interval, lnρ∼T^-3/4, contradicts the models above, too. Instead, it is found that this law can be substantiated and the correct matching of the energy and length scales can be found within a model of Fogler et al (2004 Phys. Rev. B 69 035413) by treating CaCu ₂O₃ as a three-dimensional array of quasi-one-dimensional electron crystals