We use different theoretical approaches to demonstrate the qualitative and quantitative understanding of coherent electron tunneling transport through several organic molecules. Molecules that we consider are phenylenevinylene oligomer (OPV5), carotene, dithienylethene, and xyxyldithiol. The complex bandstructure technique is useful for molecules that have repeating units, and is used here to make estimates of the conductance and its dependence on molecular length for OPV5 and for carotene (in a charge state). For molecules of a general shape, such as that of the photoswitching dithienylethenes, we use Landauer theory to predict the I-V properties. The same analysis is used to study the conductance of xyxyldithiol molecules that are deformed by stretching as in AFM pulling experiments.