The carbon-13 NMR longitudinal relaxation times (T1) studies on the 1,3-alternate-shaped calix[4]arene possessing two ester groups 1 in the absence and the presence of Na+ were carried out for the first time. The T1 values were measured under proton-noise-decoupling conditions by the inversion-recovery technique. The T1-value of 1 is primarily governed by dipole-dipole relaxation. When calixarene 1 forms an ensemble with Na, the T1-values for all carbons are decreased. This suggests that the molecular motion of species 1 is efficiently frozen through complexation with Na+. Eventually, Na+ ion plays an important role as a template ion specifically to freeze the fluctuational motion of two ethoxycarbonylmethoxybenzene units of 1. © 2006, Japan Oil Chemists' Society. All rights reserved.