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(13.2–44.7) 0.6 Self-prepared % (95%CI) 70.4 (57.2–80.9) 66.7 (47.8–81.4) 74.1 (55.3–86.8) Number of different models of e-cigarette (device) used Mean ± SD 4 ± 4 3.6 ± 3.3 4.3 ± 4.6 0.5 Median (min–max) 3 (1–23) 3 (1–17) 3 (1–23) Legend: 95%CI, 95-percent confidence interval; min–max, minimum and maximum value range; * results of U Mann-Whitney test. Dual users who were actively smoking both types of cigarettes (traditional and e-cigarette) indicated that traditional cigarette smoking offers more smoking satisfaction (46.2%) compared to using e-cigarettes (23%). Also, smoking a cigarette in a group of friends, in combination with a cup of coffee, after a meal, or after sex was associated with a greater subjective feeling of satisfaction compared to the feelings associated with the use of an e-cigarette in the same situations. Dual users indicated that the smell (92.9%) and the taste (82.1%) of e-cigarettes as well as the subjective feeling associated with the inhalation and exhalation of vapor generated from e-cigarettes were the primary advantages of e-cigarettes over traditional cigarettes. 3.2. Fagerstrom Scores and Levels of Nicotine Addiction The average FTND score among exclusive e-cigarette users was over twice as high (mean 3.5 versus 1.6) as among traditional cigarette smokers (p = 0.002; Table 2). The mean nicotine dependence level from e-cigarettes (mean 4.7) was higher than that from traditional cigarettes (mean 3.2; p = 0.03) among dual users. E-cigarette users were more likely to use an e-cigarette in the first 30 min after waking and were more likely to find it difficult to refrain from using e-cigarettes in places where it is forbidden (Table 2). Int. J. Environ. Res. Public Health 2019, 16, 2279 5 of 10 Table 2. Aspects of cigarette and e-cigarette smoking based on Fagerström test for nicotine dependence (FTND). Smokers n = 30 % (95%CI) Exclusive E-Cigarette Users n = 30 % (95%CI) Dual Users n = 30 % (95%CI) p How soon after waking up do you reach for a cigarette? Within 30 min 17.9 (7.9–35.6) 42.3 (25.5–61.1) 0.04 After 30 min 82.1 (64.4–92.1) 57.7 (38.9–74.5) How soon after waking up do you reach for an e-cigarette? Within 30 min 53.9 (35.5–71.2) 57.1 (39.1–73.5) 0.8 After 30 min 46.1 (28.8–64.5) 42.9 (26.5–60.9) Do you find it difficult to refrain from smoking in places where it is forbidden? Yes 10.7 (3.7–27.2) 19.2 (8.5–37.9) 0.4 No 89.3 (72.8–96.3) 80.8 (62.1–91.5) Do you find it difficult to refrain from use e-cigarette in places where it is forbidden? Yes 34.6 (19.4–53.8) 42.9 (26.5–60.9) 0.5 No 65.4 (46.2–80.6) 57.1 (39.1–73.5) Which cigarette would you hate most to give up? The first one in the morning 57.1 (39.1–73.5) 73.1 (53.9–86.3) 0.2 Any other 42.9 (26.5–60.9) 26.9 (13.7–46.1) Which e-cigarette would you hate most to give up? The first one in the morning 30.8 (16.5–50.0) 35.7 (20.7–54.2) 0.7 Any other 69.2 (50.0–83.5) 64.3 (45.8–79.3) How many cigarettes per day do you smoke? 10 or less 85.7 (68.5–94.3) 69.2 (50.0–83.5) 11 to 20 14.3 (5.7–31.5) 23.1 (11.0–42.1) 0.2 21–30 0.0 (0.0–11.3) 7.7 (2.1–24.1) 31 or more 0.0 (0.0–11.3) 0.0 (0.0–11.3) How many times a day do you use e-cigarettes? (Number of e-smoking sessions: one e-smoking session consist of 15 puffs or approximately 10 min of use) 10 or less 38.5 (22.4–57.5) 32.1 (17.9–50.7) 11 to 20 38.5 (22.4–57.5) 35.7 (20.7–54.2) 0.8 21–30 11.5 (4.0–28.9) 10.7 (3.7–27.2) 31 or more 11.5 (4.0–28.9) 21.4 (10.2–39.5) Do you smoke more frequently during the first hours after waking than during the rest of the day? Yes 14.3 (5.7–31.5) 34.6 (19.4–53.8) 0.08 No 85.7 (68.5–94.3) 65.4 (46.2–80.6) Do you use e-cigarettes more frequently during the first hours after waking than during the rest of the day? Yes 15.4 (6.2–33.5) 39.3 (23.6–57.6) 0.05 No 84.6 (28.8–64.5) 60.7 (42.4–76.4) Int. J. Environ. Res. Public Health 2019, 16, 2279 6 of 10 Table 2. Cont. Smokers n = 30 % (95%CI) Exclusive E-Cigarette Users n = 30 % (95%CI) Dual Users n = 30 % (95%CI) p Do you smoke if you are so ill that you are in bed most of the day? Yes 21.4 (10.2–39.5) 42.3 (25.5–61.1) 0.09 No 78.6 (60.5–89.8) 57.7 (40.0–74.5) Do you use e-cigarettes if you are so ill that you are in bed most of the day? Yes 34.6 (19.4–53.8) 67.9 (49.3–82.1) 0.01 No 65.4 (46.2–80.6) 32.1 (17.9–50.7) FTND summary score FTND cigarette score: mean ± SD 1.6 ± 1.6 3.2 ± 2.2 0.002 * FTND e-cigarette score: mean ± SD 3.5 ± 2.6 4.7 ± 2.6 0.03 ** 95%CI indicates the 95% Confidence Interval; p indicates the result of the U Mann-Whitney test; * indicates the result of the U Mann-Whitney test for smokers versus exclusive e-cigarette users; ** indicates the result of the U Mann-Whitney test for cigarettes versus e-cigarettes among dual users. 4. Discussion The results of our study allow us to characterize patterns of use of e-cigarettes among young adults in Poland who are experienced users of e-cigarettes. Almost