Ionospheric scintillation refers to the random and rapid fluctuations in the amplitude and phase of radio signals that occur due to their propagation through plasma density irregularities in the ionosphere. For Global Navigation Satellite System (GNSS), scintillation can seriously degrade satellite signal quality and consequently the positioning accuracy, particularly at high and low latitude regions, where ionospheric disturbances are more frequent. This study analyzes the effects of scintillation on Global Positioning System (GPS) Precise Point Positioning (PPP), by making use of scintillation data recorded in Hong Kong during the solar maximum of 2014. Significant positioning error values of as much as 1.34 m in the up direction are observed with kinematic PPP processing under strong scintillation. The variations in the standard deviations of the carrier phase residuals in relation to satellite elevations and scintillation levels are investigated for the first time in this region. It is found that the standard deviation of carrier phase residuals increases depending on scintillation intensity. This study is important to help better understand the scintillation characteristics and its effects on GPS-based positioning in the Hong Kong region. It can also help in modelling the relationship between scintillation and carrier phase residuals, which can be of use in the development of scintillation mitigation approaches for PPP processing.