Diamond films have been deposited on a variety of substrates up to 2 cm below the luminous plasma in a tubular microwave plasma‐enhanced chemical vapor deposition system. Depositing downstream of the plasma appears to offer several advantages over immersion of substrates in the plasma, for coating certain oxide substrates, including a reduction in substrate etching and an improvement in film uniformity, adhesion, and transparency. Furthermore, positioning substrates downstream of the plasma and adjusting their temperature with an external heater decouples the plasma and substrate parameters, facilitating studies to determine the effect of various parameters on the chemical vapor deposition diamond process. A disadvantage of downstream deposition is the decrease in the growth rate of diamond films.