Table 2. Reliability of smoking quantity/frequency: Correlations between smoking items from the smoking questionnaire and TLFB questionnaire.

	Timeline Followback
Smoking Questionnaire	Average number of cigarettes smoked between today and yesterday	Number of cigarettes smoked in past 7 days	Average number of cigarettes smoked per day	Average number of smoking days per week
“How many cigarettes did you smoke in the past 24 hours?”	.83**	.83**	.82**	.51**
“How many cigarettes did you smoke in the past 7 days?”	.82**	.86**	.87**	.49**
“What is the usual number of cigarettes you smoke in a day?”	.85**	.89**	.90**	.48**
“On average, how many days in a week do you smoke cigarettes (0–7)?”	.47**	.49**	.50**	.80**

^**.p < .01 (2-tailed).

Bold indicates items measuring the same construct.