Video communication over IP (Internet Protocol) networks has grown significantly in recent years. However, the Quality of Experience (QoE) associated with video over IP can vary dramatically. This is mainly due to bandwidth restrictions and the fluctuating Quality of Service (QoS). Investigating the perceptual effects of packet loss could lead to a better understanding of the QoE experienced by the end-user. In this paper, we present the results obtained from a series of subjective video quality tests that evaluated the quality of H.264/AVC videos distorted by several packet loss patterns. We draw some interesting conclusions concerning the impact on perceptual quality of (1) transmission-related factors such as the loss distribution and the lost pictures percentage; and (2) content-related factors such as the scene cut position in the video sequence and the spatial position of the loss in the picture.