This chapter critically reflects on the prevalent research practices in smartphone addiction research. We focus on four issues that impede the study of addictive/problematic smartphone use. The first is a focus on cross-sectional research, which limits the conclusions that can be drawn about smartphone use. Combined with the prevalent use of mediation analysis, many of these mechanisms are biased. The second and third issues centre on who participates in smartphone addiction research. The field is internationally diverse but systematically undersamples certain groups: adults outside of the student population, especially older adults, and people seeking treatment for smartphone addiction. These create risks of measurement biases and impede the development of robust assessment tools. Finally, the field relies heavily on self-report measures of smartphone behaviour, which appear inaccurate and difficult to defend in light of the ease of collecting this data from phones.