In this article we explore the relationship between the plasma-phase chemistry and deposit in the plasma deposition of acrylic acid. This is achieved through systematic variation of some of the plasma deposition variables, termed "processing parameters." The surface chemical composition of deposits has been investigated by means of x-ray photoelectron spectroscopy. Changes in the surface chemical composition with the ratio of plasma power-to-monomer flow rate, P/phi, substrate position tin the reactor), nature of the substrate, and washing and aging (of the deposit) are examined. Based on these, we provide a qualitative description of the deposits' molecular structure, and how this changes with P/phi. The plasma-phase chemistry has been probed by means of mass spectrometry and attention given to the effect of P/phi on the neutral and ionic components of the plasma. The major plasma-phase reactions are elucidated, and a knowledge of these help to explain how the molecular structure of plasma deposits are affected by P/phi and other processing parameters.