Composer and music tutor, he studied composition with Piotr Perkowski and Romuald Twardowski in the State Higher School of Music in Warsawster's degree in 1974). In 1980-1981, thanks to a French government scholarship, he completed postgraduate composition under Olivier Messiaen in Paris. Since 1974 he has taught theory in Józef Elsner State Secondary Music School in Warsaw. He is currently a professor in the Department of Art Education of Kazimierz Wielki University in Bydgoszcz. Since 2012 he is the president of Warsaw Department of Polish Composers' Union.

He is the winner of 17 national and international competitions for composers. Some of his more important prizes include: in 1973 - 1st prize in a competition for didactic works for Piano Concerto for Young People No.1 op. 6 (1973), in 1975 – 2nd prize in the Composer Competition of the 9th Festival of Polish Piano Art in Słupsk for Concertino per pianoforte e orchestra op. 9 (1975), in 1976 – 1st prize in the Young Composers' Competition of the Polish Composers' Union for Gradito per orchestra op. 12 (1976), in 1980 - an honourable mention in the 19th Concorso Internazionale di Composizione "Premio Cittá di Trieste" for Concerto pesante per tuba e orchestra op. 14 (1978), in the same year - Darmstadt City Award in the Chopin-Gesellschaft Competition for Symphonia concertante per pianoforte e orchestra op. 16 (1979), twice the 1st price in the Competition of the Warsaw Section of the Polish Composers' Union - in 1982 for Intrada, Elegy and Postlude for organ op. 19 (1982) and in 1985 – for Orpheus Songs for counter-tenor, flute, oboe and harp op. 24 (1985), in 1986 - the Bucchi Award in Rome for Five Pieces for Piano for Children - Forest Roaming op. 25 (1985), in 1992 - 3rd prize in the Karol Szymanowski Competition for Composers for Music from Zawrat for double-bass and piano op. 31 (1991), in 1997 – Gdańsk City Award in the 1000th Anniversary Competition for Hymnus Gedanensis - symphonic poem for mixed choir and great symphony orchestra op. 36 (1986-97).

Czarnecki's 50 numbered opuses include solo, chamber, symphonic and vocal- instrumental music. Some of the major works: Piano-trio op.12, Sonate funebre for violin and piano op.19, Via Crucis for organ op.31, Concerto pesante for tuba and orchestra op.13, Concerto for double-bass and strings op.28, Jasna Góra Mass for soprano, bass, choir and orchestra op.37. He also composes music for fhe theatre, radio and film.

Czarnecki's oeuvre can be roughly subdivided into three periods:

the youthful works composed under a distinct neo-Classical influence (2 Toccatas for piano op.4)
the period of artistic quest, in which structural thinking was dominant (Gradito per orchestra op.11, Piano-trio op.12)
the third (beginning with Via Crucis per organo op.31, and Hombark-concerto op.32), in which the composer more openly refers to tradition, both adopting the germs of Polish folklore (Scepus-Quartetto op.33, Wałaski op 35, Concerto Liliowe op.41, Concerto Lendinum op.44), and drawing on great religious traditions, at the centre of which was the Gregorian Chant ( Jasna Góra Mass op.37, Corona Mariae- Hymni for choir op.45).
Sławomir Czarnecki might well say about his music what the eminent French composer Francis Poulenc once said about his: "I know perfectly well that I am not one of those composers who introduce harmonic innovations, like Stravinsky, Ravel or Debussy, but I believe there is also room for the kind of music that unashamedly makes use of borrowed chords. Was it not the case with Mozart or Schubert?" Sławomir Czarnecki has never been an avant-garde artist, and the less so recently, when he has come close to what he describes as "after-modern aesthetics". In this aesthetics, he writes works which are transparent in texture and clear in form, easy to understand and providing the audience with many joyful moments. These works are satisfying to musicians as well, which is borne out by the performances of such pieces as Hombark-Concerto for violin and string orchestra or the "Lily-Coloured" Concerto for two violins and string orchestra. The soloist, the excellent violinist Krzysztof Jakowicz clearly derived much pleasure and fun from playing those compositions. The highlander rhythms of both concertos provoked him to move on the stage in nearly dance-like steps. The "Lily-Coloured" Concerto, first performed by Krzysztof Jakowicz with his son Jakub in Polish Radio Witold Lutosławski Concert Studio was encored - a rare success for a contemporary work.

Czarnecki visibly establishes contact with the audience - perhaps what helps him to achieve this is the regular contact with the young people whom he teaches composition? This composition study on the level of secondary school is, by Polish standards, an exceptional situation, as the norm here is to teach composition in academies on the highest level of formalised music education. Czarnecki himself opened an "Introduction to Composition" class in the State Music School No. 1 in Warsaw, and his pupils have in recent years won a total of 18 prizes in national and international competitions for young composers. In this, they imitate their master, as Sławomir Czarnecki is the winner of 17 composer competitions at home and abroad, as it was carefully calculated in the programme of a Polish Composers' Union concert in December 2002, where three of his pieces were performed.