A new generation of high-performance, time-of-flight (TOF) PET scanners have recently been developed. In earlier works, the gain with TOF information was derived as a reduction of noise in the reconstructed image, or essentially a gain in scanner sensitivity. These derivations were applicable to analytical reconstruction techniques and 2D PET imaging. In this work, we evaluate the gain measured in the clinically relevant task of lesion detection with TOF information in fully 3D PET scanners using iterative reconstruction algorithms. We performed measurements in a fully 3D TOF PET scanner using spherical lesions in uniform, cylindrical phantom. Lesion detectability was estimated for 10 mm diameter lesions using a non-prewhitening matched filter signal-to-noise-ratio (NPW SNR) as the metric. Our results show that the use of TOF information leads to increased lesion detectability, which is achieved with less number of iterations of the reconstruction algorithm. These phantom results indicate that clinically, TOF PET will allow reduced scan times and improved lesion detectability, especially in large patients.