The Poisson's ratio of carbon nanotube (CNT) dry-spun yarns can be tuned over an extremely wide range of values that are up to 20-30 times higher than common solid materials. This is a result of the highly variable porosity of the yarn structure, from 90% in very low twist yarns to 40% in high twist yarns. The change of CNT geometry during the conversion from forest to web also plays an important role in the formation of CNT bundles and consequently influences the CNT dry-spun yarn structure. The CNT dry-spun yarn achieved its maximum specific strength when the CNTs on the yarn surface formed a 20° angle to the yarn axis. These CNT dry-spun yarn structure-property relationships can be utilized in the design of different applications, such as tuning the sensitivity of sensors and the functional characteristics of CNT composites.